PI: Gordon, Vernita Title: Assessing the roles of biofilm structure and mechanics in pathogenic, 

persistent infections

Received: 11/07/2016 FOA: PAR16-242 Council: 05/2017

Competition ID: FORMS-D FOA Title: BIOENGINEERING RESEARCH GRANTS (BRG) (R01)

1 R01 AI121500-01A1 Dual: Accession Number: 3992249

IPF: 578403 Organization: UNIVERSITY OF TEXAS, AUSTIN

Former Number: Department: Physics

IRG/SRG: BMBI AIDS: N Expedited: N

Subtotal Direct Costs Animals: Y New Investigator: Y

(excludes consortium F&A) Humans: N Early Stage Investigator: N

Year 1: Clinical Trial: N

Year 2: Current HS Code: 10

Year 3: HESC: N

Year 4:

Senior/Key Personnel: Organization: Role Category:

Vernita Gordon The University of Texas at Austin PD/PI 

Kendra Rumbaugh Texas Tech University Health Science 

Center

Other (Specify)-Collaborator

Christopher Gordon Texas Tech University Other (Specify)-Collaborator

Jason Shear PhD The University of Texas at Austin Other (Specify)-Collaborator

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Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

OMB Number: 4040-0001

Expiration Date: 06/30/2016

APPLICATION FOR FEDERAL ASSISTANCE

SF 424 (R&R)

1. TYPE OF SUBMISSION*

❍Pre-application ●Application ❍Changed/Corrected

Application

2. DATE SUBMITTED

2016-11-07

Application Identifier

201603679-001

3. DATE RECEIVED BY STATE State Application Identifier

b. Agency Routing Number

4.a. Federal Identifier

AI121500

c. Previous Grants.gov Tracking Number

5. APPLICANT INFORMATION Organizational DUNS*:

Legal Name*: The University of Texas at Austin

Department: 

Division: 

Street1*: 

Street2: 

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County: 

State*:

Province: 

Country*:

ZIP / Postal Code*:

Person to be contacted on matters involving this application

Prefix: First Name*: Sofia Middle Name: I. Last Name*: Zanabria Suffix: 

Position/Title: Grants & Contract Specialist

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6. EMPLOYER IDENTIFICATION NUMBER 

7. TYPE OF APPLICANT*

Other (Specify):

Small Business Organization Type ❍Women Owned ❍Socially and Economically Disadvantaged

8. TYPE OF APPLICATION*

Fax Number: Email:

(EIN) or (TIN)* 

H: Public/State Controlled Institution of Higher Education

❍New ●Resubmission

❍Renewal ❍Continuation ❍Revision

If Revision, mark appropriate box(es).

❍A. Increase Award ❍B. Decrease Award ❍C. Increase Duration

❍D. Decrease Duration ❍ E. Other (specify) :

Is this application being submitted to other agencies?* ❍Yes ●No What other Agencies?

9. NAME OF FEDERAL AGENCY*

National Institutes of Health

10. CATALOG OF FEDERAL DOMESTIC ASSISTANCE NUMBER

TITLE:

11. DESCRIPTIVE TITLE OF APPLICANT'S PROJECT*

Assessing the roles of biofilm structure and mechanics in pathogenic, persistent infections

12. PROPOSED PROJECT

Start Date* Ending Date*

05/01/2017 04/30/2021

13. CONGRESSIONAL DISTRICTS OF APPLICANT

TX-025
Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

Contact PD/PI: Gordon, Vernita

SF 424 (R&R) APPLICATION FOR FEDERAL ASSISTANCE Page 2

14. PROJECT DIRECTOR/PRINCIPAL INVESTIGATOR CONTACT INFORMATION

Prefix: First Name*: Vernita Middle Name: Last Name*: Gordon Suffix: 

Position/Title: Assistant Professor 

Organization Name*: The University of Texas at Austin

Department: 

Division: 

Street1*: 

Street2: 

City*: 

County: 

State*:

Province: 

Country*:

ZIP / Postal Code*:

Phone Number*: Fax Number: Email*:

15. ESTIMATED PROJECT FUNDING 16.IS APPLICATION SUBJECT TO REVIEW BY STATE 

EXECUTIVE ORDER 12372 PROCESS?*

a. Total Federal Funds Requested*

b. Total Non-Federal Funds*

c. Total Federal & Non-Federal Funds*

d. Estimated Program Income*

a. YES ❍ THIS PREAPPLICATION/APPLICATION WAS MADE 

AVAILABLE TO THE STATE EXECUTIVE ORDER 12372

PROCESS FOR REVIEW ON:

DATE: 

b. NO ● PROGRAM IS NOT COVERED BY E.O. 12372; OR

❍ PROGRAM HAS NOT BEEN SELECTED BY STATE FOR 

REVIEW 

17. By signing this application, I certify (1) to the statements contained in the list of certifications* and (2) that the statements herein 

are true, complete and accurate to the best of my knowledge. I also provide the required assurances * and agree to comply with 

any resulting terms if I accept an award. I am aware that any false, fictitious, or fraudulent statements or claims may subject me to

criminal, civil, or administrative penalties. (U.S. Code, Title 18, Section 1001)

●I agree* * The list of certifications and assurances, or an Internet site where you may obtain this list, is contained in the announcement or agency specific instructions.

18. SFLLL or OTHER EXPLANATORY DOCUMENTATION File Name:

19. AUTHORIZED REPRESENTATIVE

Prefix: First Name*: Courtney Middle Name: Last Name*: Frazier Swaney Suffix: 

Position/Title*: Associate Director

Organization Name*: The University of Texas at Austin

Department: 

Division: 

Street1*: 

Street2: 

City*: 

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State*:

Province: 

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ZIP / Postal Code*:

Phone Number*: Fax Number: Email*:

Signature of Authorized Representative* Date Signed*

20. PRE-APPLICATION File Name:

21. COVER LETTER ATTACHMENT File Name:Cover_Letter1027054231.pdf
Contact PD/PI: Gordon, Vernita

Project/Performance Site Location(s)

OMB Number: 4040-0010

Expiration Date: 06/30/2016

Project/Performance Site Primary Location ❍I am submitting an application as an individual, and not on behalf of

a company, state, local or tribal government, academia, or other type of 

organization.

Organization Name: The University of Texas at Austin

Duns Number: 

Street1*: 

Street2:

City*: 

County: 

State*: 

Province: 

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Zip / Postal Code*:

Project/Performance Site Congressional District*: TX-025

File Name

Additional Location(s)

Page 4

Tracking Number: GRANT12284250 Funding Opportunity Number: PAR-16-242. Received Date: 

2016-11-07T15:37:27.000-05:00
Contact PD/PI: Gordon, Vernita

RESEARCH & RELATED Other ProjectInformation

OMB Number: 4040-0001

Expiration Date: 06/30/2016

1. Are Human Subjects Involved?* ❍ Yes ● No

1.a. If YES to Human Subjects

Is the Project Exempt from Federal regulations? ❍ Yes ❍ No

If YES, check appropriate exemption number: 1 2 3 4 5 6 If 

NO, is the IRB review Pending? ❍ Yes ❍ No

IRB Approval Date:

Human Subject Assurance Number

2. Are Vertebrate Animals Used?* ● Yes ❍ No

2.a. If YES to Vertebrate Animals

Is the IACUC review Pending? ❍ Yes ● No 

IACUC Approval Date: 05-30-2016

Animal Welfare Assurance Number

3. Is proprietary/privileged information included in the application?* ❍ Yes ● No

4.a. Does this project have an actual or potential impact - positive or negative - on the environment?* ❍ Yes

4.b. If yes, please explain:

4.c. If this project has an actual or potential impact on the environment, has an exemption been authorized or an ❍ Yes

environmental assessment (EA) or environmental impact statement (EIS) been performed?

4.d. If yes, please explain:

● No

❍ No

5. Is the research performance site designated, or eligible to be designated, as a historic place?* ❍ Yes ●

5.a. If yes, please explain:

No

6. Does this project involve activities outside the United States or partnership with international ❍ Yes ●

collaborators?*

6.a. If yes, identify countries:

6.b. Optional Explanation:

No

Filename

7. Project Summary/Abstract* Project_Summary_and_Abstract1026881782.pdf

8. Project Narrative* Project_Narrative1026881781.pdf

9. Bibliography & References Cited 2016_11_06_references1027054170.pdf

10.Facilities & Other Resources Facilities_and_other_resources combined1026881827.pdf

11.Equipment EQUIPMENT Gordon1026881826.pdf

12. Other Attachments Christopher G letter_of_commitment_signed_11_4_161027054119.pdf

Rumbaugh_LOI1027054120.pdf

Page 5

Tracking Number: GRANT12284250 Funding Opportunity Number: PAR-16-242. Received Date: 

2016-11-07T15:37:27.000-05:00
Contact PD/PI: Gordon, Vernita

Project Summary/Abstract Page 6

What spatial structure and mechanics develops in biofilm infections, and how such spatial structure and 

mechanics impact the persistence and virulence of biofilm infections, is not known. The long-term goal is to 

find diagnostic and treatment approaches that address the structure and mechanics of multicellular, threedimensional biofilm infections within the host. The objective of this proposal is to determine the mechanics and 

structure of biofilm infections of the opportunistic pathogen Pseudomonas aeruginosa in chronic wounds, and 

how these physical properties impact disease course. The central hypothesis is that spatial structure and 

mechanics are the major physical factors controlling virulence, antibiotic resistance, and immune evasion in 

biofilm infections. The rationale underlying this proposal is that completion will identify key physical targets for 

preventing, disrupting, or ameliorating biofilm infections for an important biofilm-forming pathogen. The 

proposed work will also develop a widely-applicable platform for assessing the state and impact of biofilm 

structure and mechanics for other infecting organisms. The central hypothesis will be tested by pursuing three 

specific aims: 1) Determine the spatial structure and mechanics of in vivo biofilm infections; 2) Determine how 

spatial arrangements differentiate into distinct microenvironments; 3) Determine the role of spatial structure 

and mechanics in biofilm-neutrophil interactions. We will pursue these aims using an innovative combination 

of analytical and manipulative techniques from both biological and physical sciences. These include both 

recently-developed techniques specific to biofilm studies, and more-established techniques that have been 

applied very little to the study of biofilm materials. The proposed research is significant, because it will 

determine which structural and mechanical characteristics should be therapeutic targets. It is also significant 

because it will develop a platform that can be extended to study other pathogens (or commensals) and 

synergies to open new avenues for biofilm therapies. This work will develop foundational resources that will be 

used by other researchers, for P. aeruginosa and other organisms. The proximate expected outcome of this 

work an understanding of which biofilm structural and mechanical characteristics contribute to clinical impact. 

The results will have an important positive impact immediately because they will establish better understanding 

of biofilm infection, virulence, and resistance to antibiotics and the immune system for an important pathogens, 

and long-term because they lay the groundwork to develop a suite of techniques for better treatment of biofilm 

infections.
Contact PD/PI: Gordon, Vernita

Project Narrative Page 7

The proposed research is relevant to public health because understanding what biofilm 

structures and mechanics exist and the degree to which they influence the medical outcomes of 

biofilm infections is expected to give rise to new types of treatments and diagnostics for chronic 

biofilm infections that specifically target structure and mechanics. Thus, this proposal is

relevant to the part of NIH’s mission that pertains to fostering fundamental creative discoveries 

and innovative research strategies as a basis for ultimately protecting health.
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 8 

Description of University of Texas: The University of Texas at Austin, founded in 1883, is the 

flagship campus of the University of Texas system and is a world-class center for basic and 

translational research. The Center for World University Rankings released the inaugural list of the 

world's top 100 universities and ranked UT Austin number 30. The university employs about 24,000 

faculty and staff, enrolls about 51,000 students and confers 12,000 degrees each year. Research 

funding for the 2009-2010 academic year topped $644 million and the amount awarded has 

increased each year. About $1.1 billion was awarded in sponsored research over the past two years 

and the university recovered $40 million in the past two years in revenue from the licensing of 

university technology from about 800 patents that have been awarded. UT Austin runs one of world’s 

fastest supercomputers and one of the most powerful lasers as examples of the vibrant research 

environment on campus. This environment has fostered the careers of UT Austin faculty, who have 

been distinguished nationally and internationally and includes winners of the Nobel Prize, Pulitzer 

Prize, National Medal of Science and the Wolf Prize.

Vernita D. Gordon

Institutional Commitment: Dr. Gordon has a tenure-track appointment as assistant 

professor at the University of Texas at Austin. Institutional startup funds came with this appointment 

and were used in taking the preliminary data shown in this proposal, as were supplementary funds 

from internal graduate and undergraduate research fellowships used to support the graduate and 

undergraduate students who have been working on this project (stipend and supplies). UT Austin 

has provided two years of summer salary support to allow time dedicated solely for research, lab 

space as described below, and shared facilities and equipment also as described below. The 

graduate students who took the preliminary data in this proposal have been supported on a 

combination of internal fellowship, teaching, and startup funds. Administrative support is provided 

through the University, the College of Natural Sciences, the Department of Physics, and the Center 

for Nonlinear Dynamics. Access to shared and core facilities is described below. Dedicated travel 

funds in the startup package were used to allow the PI to attend grant-writing workshops held by NIH 

and NSF. Research personnel in Professor Gordon’s group currently are 1 postdoc (PhD in 

Microbiology), 6 graduate students (5 in the Physics program at UT Austin, 1 in the Microbiology 

program at UT Austin), and numerous undergraduates.

Laboratory: Dr. Gordon’s group has approximately 1500 square feet of lab space in the 

Department of Physics in the Robert Lee Moore Hall (RLM) at the University of Texas at Austin, and 

approximately 2000 additional square feet across the street in the Neuro-Molecular Sciences (NMS) 

building. The total lab space includes one large (2 microscopes) and 1 small specially-designed 

microscopy rooms (filtered air, light-tight, and temperature control) in RLM and an additional 

microscopy room in NMS, wet lab facilities for sample preparation in both RLM and NMS, and a MilliQ pure water production system. Small equipment in the labs includes a Milli-Q pure water 

production system, a -80 freezer shared with one other biological physics faculty (Florin), -20 and -5 

freezers, refrigerators, incubators, centrifuge, spectrophotometer, and vortexer as well as other small 

equipment and supplies. Additional small equipment for biophysical and biological work is ready 

available through colleagues in the Center for Nonlinear Dynamics, the Institute for Cell and 

Molecular Biology, and the Department of Biomedical Engineering.

FACILITIES AND RESOURCES: The University of Texas at Austin (Gordon and Shear)
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 9 

Computer: Dr. Gordon has a laptop with docking station, external monitor, and external 

keyboard and mouse in her office. In Dr. Gordon’s lab are three instrument computers, one to control 

each microscope, and a Linux server purpose-built for rapid image processing and analysis. This 

server runs doubly-redundant RAID. The group has a second Linux server dedicated to automated 

data backup. We do a second automated backup to tape, for long-term, off-site storage through the 

Texas Advanced Computing Center. The group has an additional desktop computer currently used 

by Dr. Gordon’s postdoc and multiple personal laptops. The Gordon group has its own licenses for 

IDL and for Kaleidograph. UT Austin provides free copies of the Microsoft Office suite to students, 

faculty, and staff. Through the Center for Nonlinear Dynamics (see below), the group has access to 

Matlab site licenses and Adobe products. Offices and labs are all equipped with multiple Ethernet 

ports as well as wireless Internet access. Computer support is provided by University, Department, 

and CNLD IT staff.

Clinical: N/A

Animal: N/A

Office: Dr. Gordon has a 200 square foot office. Graduate students each have their own 

desks in shared offices. Undergraduates share desk space as appropriate. In addition, the Center 

for Nonlinear Dynamics has a seminar room for regular meetings and seminars. All the office space, 

the RLM lab space (including both microscopy rooms) and the seminar room are on the same floor; 

this greatly facilitates group interaction. Having the NMS space directly across the street makes 

regular traffic back and forth straightforward, and helps facilitate contact with microbiological 

colleagues also located in the NMS building. Through the Center for Nonlinear Dynamics (CNLD – 

see below), the group has access to Matlab site licenses and to Adobe Photoshop and other Adobe 

products. The group has its own licenses for IDL and for Kaleidograph. UT Austin provides free 

copies of the Microsoft Office suite to students, faculty, and staff. Offices and labs are all equipped 

with multiple Ethernet ports as well as wireless Internet access. There are CNLD shared printers 

(color and B/W), scanner, fax, and copier. Computer support is provided by University, Department, 

and CNLD IT staff.

Other Resources:

Support: PI Vernita Gordon is a member of the Center for Nonlinear Dynamics, a strength of 

UT Austin’s physics department. The Center for Nonlinear Dynamics (CNLD) provides administrative 

support (administrator and an assistant), computer network infrastructure, and a visiting scientist 

program with typically 25 visitors/year. The CNLD has a well-established infrastructure for the 

education of students and postdocs with lecture courses, a weekly Nonlinear Dynamics Seminar, and 

a weekly group meeting (http://chaos.utexas.edu/talks). Every student has to present his/her project 

and results at regular intervals (at least once a year); students are strongly encouraged to practice 

their talks in front of a few critical peers before speaking before the full group. Group meetings are 

attended by all Center students, postdocs, and faculty (Swinney, Marder, Raizen, Swift, McCormick, 

Florin, Gordon). The weekly seminars also draw faculty and students from Microbiology, Physics, 

Mathematics, and Engineering. The biological physics groups in the CNLD (Gordon, Florin) also have 

a weekly journal club at which students and postdocs present recent relevant journal articles and 

distribute recent papers of interest.

Secretarial and administrative services are also provided by the Physics department.
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 10

The Center for Systems and Synthetic Biology (CSSB) has a regular (approximately biweekly) lunch 

for faculty interested in complex biological systems, such as the effects of population structure 

examined in this proposal. Gordon is a participant and speaker in these lunches, at which faculty 

members present current research in their groups. Over thirty other faculty participate in these 

lunches.

The PI is a member of the Institute of Cellular and Molecular Biology (ICMB) and has access to the 

Institute core facilities, described below. The ICMB has a regular seminar series with external 

speakers. The PI is a member of the Graduate Studies Committees for both Cellular and Molecular 

Biology and Microbiology and Molecular Genetics, and as such can supervise PhD students from 

both programs. This provides the group with infusions of fresh perspectives and skills. Currently, two 

members of the Gordon group are graduate students in the Microbiology program.

Jason B. Shear

Laboratory: The Shear laboratory occupies several rooms in the Welch Chemistry Building, and 

consists of ~2500 sq. ft. of wet lab, optical lab, and cell culturing facilities.

Computer: The Shear group uses numerous recent incarnations of Macintosh and PC computers for 

collecting and analyzing data and writing manuscripts. Image analysis is performed using a 

commercial package (Metamorph) and ImageJ shareware.

Clinical: N/A

Animal: N/A

Office: Dr. Shear maintains an office near his laboratories. In addition to the PI's office, office space 

exists for ~10 students including commons areas for meeting and discussing experimental plans and 

results. 

Advanced Imaging: The Shear lab has access to various high-end imaging systems through users 

facilities in the Institute for Cellular and Molecular Biology and the Biomedical Engineering

Department. These include an Asylum Research AFM with MFP3D software for both contact-mode 

imaging and force measurements, a FEI Tecnai transmission electron microscope, and several 

confocal fluorescence microscopes.

Other: Within Shear’s laboratory or building is an ultrapure water system, ice-machines, a

spectrophotometer, a fluorimeter, shaking incubators, a –80°F freezer, and several wide-field 

fluorescence microscopes. User and staff facilities in Welch Chemistry building or nearby provide 

access to scanning confocal laser microscopy, deconvolution microscopy, a time-resolved 

fluorimeter, mass spectrometry, machining, glass blowing, electronics design/repair, and high-field 

NMR. University facilities also exist for peptide and nucleic acid synthesis/analysis, scanning electron 

microscopy, and transmission electron microscopy. Dr. Shear is provided with administrative

assistance and has access to fax and photocopier services. 

Core Facilities at UT Austin (available to both Gordon and Shear)

Core Facilities: The University of Texas at Austin operates core facilities dedicated to providing the 

latest equipment and knowledge necessary to assist researchers on campus. From routine, though
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 11

essential, support services to advanced technical and consulting services, these cores facilitate and 

enhance the important research conducted at the university on a daily basis. The available core 

facilities are listed as follows.

 College of Liberal Arts/College of Natural Sciences Facilities.

• Imaging Research Center.

• Institute for Cellular and Molecular Biology (ICMB) Core Research Facilities. The 

ICMB core facilities support cellular and molecular biology research at The University of 

Texas at Austin. The facilities offer a full range of services in nucleic acid and protein 

sequencing, x-ray crystallography, and transgenic-knockout mice. The core facilities are 

open on an equal basis to all faculty with a philosophy to keep the core facilities as 

comprehensive and accessible as possible to increase faculty, staff, and student research 

productivity. The individual facilities are listed below.

 DNA sequencing & Genomics Facility.

 The Protein and Metabolite Analysis facility

 UT Microarray Facility. Administered through the Center for Systems and Synthetic 

Biology (see above).

 Microscopy Core Facility. This core facility is the most likely to be used for this 

project as it contains widefield (Zeiss Axiovert 200 M) and confocal (Leica SP2 

AOBS) fluorescent microscopes as well as software for data processing and 

analysis, including Imaris (used to prepare the topographic views shown in this 

proposal) and Metamorph.

 Macromolecular Crystallography Facility.

• Department of Chemistry and Biochemistry. The Department of Chemistry & 

Biochemistry features a variety of in-house services and facilities that support state-of-theart teaching activities and high-level scientific research. Laboratory and classrooms are 

housed in over 500,000 sq. ft. of modern space and the department has numerous 

innovative resources to propel ground-breaking research. Individual facilities are listed 

below.

 Center for Electrochemistry. 

 Mass Spectrometry.

 Nuclear Magnetic Resonance.

 Welch Computer Lab.

 X-Ray Facility.

 Fisher Scientific Research Storeroom.

 Glassblowing Shop.

 Instructional Medial Laboratory.

 Instrument Design and Repair.

 Machine Shop.

 College of Pharmacy. The College of Pharmacy offers access to core facilities to the 

researchers on campus. These facilities are listed below.

• Protein and Metabolite Analysis Facility.

• Drug Dynamics Institute: InstrUcTex Core.

 Texas Institute for Drug and Diagnostics Development.
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 12

 Automation and High Throughput Screening Facility.

 Genomic Sequencing and Analysis Facility.

 Macromolecular Crystallography Facility.

 Materials Physics Laboratory.

Laboratory:

Equipment available in the Dr. Rumbaugh’s laboratories include laminar flow hoods for tissue culture, 

CO2 incubators, bacterial incubators, high-speed refrigerated centrifuges with rotors, refrigerated 

microfuges, gel electrophoresis equipment and power supplies, orbital-shaking water baths, 

spectrophotometers and a luminometer, a monochromator-based multi-mode microplate reader for 

fluorescence and luminescence, analytical balances; autoclaves and drying ovens, –20oC and –80oC 

freezers, fridges, liquid nitrogen storage tank and thermocyclers for PCR.

Additional Facilities available at TTUHSC:

Dr. Rumbaugh has joint appointments in the Depts of Cell Biology and Biochemistry and Microbiology 

and Immunology. Additional equipment available in the Department of Microbiology and Immunology 

include an ABI7000 real time PCR machine, a Typhoon phosphor-imager and and gel imaging 

equipment. Specific to this project, the SilhouetteStar laser scanning wound imaging, 3D 

measurement and documentation system, will be used to document wound area and volume. The 

SilhouetteStar is a shared resource in the Department of Surgery. A Nikon TiE confocal microscope, 

which is equipped with an option known as N-STORM (Nikon Stochastic Optical Resolution 

Microscopy) is available in the Imaging Core and will be used for the described imaging studies.

Institutional Commitment to ESI: Assistant Professor Christopher has strong support from Texas 

Tech University to conduct research as part of his tenure track appointment. His startup package as 

an assistant professor at Texas Tech University in the Mechanical Engineering Department included 

a major renovation of the room ME 133 bd, turning it into 400 ft2 of brand new laboratory space and 

giving him funds to purchase a rheometer, inverted microscope and high speed camera all of which 

are necessary to complete the proposed work. Furthermore, Christopher currently has 3 PhD 

students supported by startup funds, teaching assistantships, and through additional support provided 

by the Graduate School Dean’s office. As part of his assigned duties, Christopher focuses 65% of 

his time towards research related activities per the university’s guidance. Christopher has access to 

the TTU Materials Characterization Center (described below) which offers a number of tools for 

visualizing soft matter. Finally, through the Texas Tech Teaching, Learning and Professional 

Development Center, the PI has access to training in grant writing, budgeting, ethics, and other 

faculty development programs.

FACILITIES AND RESOURCES: Texas Tech University Health Sciences Center (Rumbaugh)

FACILITIES AND RESOURCES: Texas Tech University (Christopher)
Contact PD/PI: Gordon, Vernita

Facilities & Other Resources Page 13

Christopher Laboratory: Microfluidics and Microrheology: Christopher’s primary lab space is the 

newly renovated ME 133 bd. It is 400 ft2 of brand new laboratory space. The renovation included 

new water lines, sufficient power requirements, house air and nitrogen lines, and new safety showers 

and eyewashes. The laboratory has been outfitted with a 64 ft2 class 10,000 modular clean room 

with UV filtering windows. The clean room is also outfitted with a fume hood for chemical work. Safe 

and sufficient storage, including a fire safe cabinet and a fridge, are available in the laboratory. 

Balances, ovens, UV exposure lamp, spinner, plasma cleaner, sonicator, stir plates and glassware for 

chemical work and solution prep have also been purchased and are ready for use.

Computer: The lab space is outfitted with 2 desktops and a lap top for data analysis, and a 

ReadyNAS Pro 6 level 5 Raid server for file backup and access over the internet. The College of 

Engineering IT-Division led by Nick Rinker who provides technical support and repairs to all 

computers in the laboratory facilities. Christopher, through the college of engineering, has access to 

licenses for Matlab, Microsoft Office, and Autocad software.

Office: Christopher has separate office space for himself and his graduate students to conduct nonexperimental work and space for writing, reading and other activities. These offices are located in the 

same building as the laboratory space. Christopher has access to the administrative staff of the 

department of Mechanical engineering to assist in various administrative tasks. 

Other Resources:

Intellectual Resources: Christopher is a member of 2 interdisciplinary faculty groups that provide a 

robust and helpful community for collaboration and high level academic discussions. The Complex 

Fluids Group is a weekly gathering of professors and students to present ongoing research, practice 

conference talks, and educational talks. This group provides a means of vetting early work, 

discussing possible problems and interpreting results. Of particular note in this group is Dr. Raj 

Khare of Chemical Engineering who has a background in simulating the rheology of confined 

biological soft matter and whose insight will provide great help to the proposed research. The Soft 

Matter group is a weekly meeting of professors working in soft matter to present their work, look for 

possible collaborations and identify possible large group funding sources. 

TTU Materials Characterization Center: The center is designed to support and complete a range of 

materials studies from synthesis to characterization and includes the following equipment: atomic 

force microscope, spinning disc confocal microscope, differential scanning calorimeter, scanning 

electron microscope, fourier transform infrared spectrometer, microspore analyzer, and x-ray 

diffracomteter. The center is staffed by a technician who provides training and support.
Contact PD/PI: Gordon, Vernita

Equipment Page 14

Major equipment available for this project

Our laboratories are fully equipped to perfrom the experiments described here, either using 

equipment physically located in our laboratories or through the use of shared equipment, either in 

institutional or departmental core facilities. Breakdown by participant follows:

GORDON (UNIVERSITY OF TEXAS AT AUSTIN)

The primary equipment to be used in this proposal are existing microscopes and a Linux server for 

data analysis. The server is described in the Facilities statement.

An inverted confocal epifluorescent laser-scanning microscope (Fluoview, Olympus) will be 

used on this project. The confocal microscope has three photomultiplier tubes for imaging as well as 

multiple laser lines, for which the 488 and 543 lines will likely be the most used on this project. This 

allows imaging and spectral resolution of GFP, YFP, and propidium iodide (PI) dead-stain 

fluorescence, with additional laser lines and filters available should the need arise.

A second inverted Olympus microscope is equipped with laser tweezers as well as 

epifluorescent, brightfield, and phase contrast imaging, and was used to acquire preliminary data 

shown in this proposal. The group has fluorescent filter cubes for GFP, YFP, and PI imaging, and 

can acquire additional filter cubes as needed.

Imaging on both microscopes is software-controlled, allowing long-term, automated data 

acquisition. The confocal microscope uses photomultiplier tubes and for the other microscope we 

have both a QImaging Blue camera and an Orca Flash 4.0 camera. The latter is a scientific CMOS 

camera with over 70% quantum efficiency at 600 nm, low noise (1.3 electrons at 100 frames/sec), 4 

megapixels (with 6.5x6.5 μm pixels), and capable of 100 frames/sec at full resolution.

Each microscope has a temperature- and humidity-controlled enclosure. The enclosures 

(Precision Plastics) maintain temperature adjustable from room (~20 °C) up to greater than 50 °C, 

and stable to within 0.1 °C over days. This allows long-term incubation on the microscope at 

physiological temperatures. There is also a temperature-controlled stage insert and objective 

heating/cooling collar that can be switched between the two microscopes to allow more-localized 

control of sample temperature. As well as two low-magnification 10x air objectives and a mediummagnification 40x air objective, there are two 100x oil objectives, a 60x oil objective, and a 60x air 

objective. All are from Olympus and fully sharable between all microscopes. Our primary intention is 

to use the 100x and 60x oil objectives in this study, along with the 60x air objective. This will allow 

high-resolution imaging of single-cell behavior and early structural development, and will allow 

measurements of the localization (and through this, the structural dependence) of antibiotic 

resistance and virulence gene expression. As needed, lower-magnification objectives can be used to 

image a larger area of biofilm structure.

Other equipment used in this proposal will be the microbiological storage, culture, and 

characterization equipment in the PI and collaborators’ laboratories. These include -80 freezer, 

shaking and stationary incubators, spectrophotometers, 96 well plate reader, electroporation 

apparatus, electrophoresis apparatus, PCR thermocyclers, and other items detailed in the Facilities 

and Other Resources statement.

RUMBAUGH (TEXAS TECH UNIVERSITY HEALTH SCIENCES CENTER)

Dr. Rumbaugh’s laboratories are fully equipped to perfrom the experiments described here, either 

using equipment physically located in their laboratories or through the use of shared equipment,
Contact PD/PI: Gordon, Vernita

Equipment Page 15

either in institutional or departmental core facilities. Dr. Rumbaugh has joint appointments in the

Depts of Cell Biology and Biochemistry and Microbiology and Immunology. Equipment available in 

the PI’s laboratories include laminar flow hoods for tissue culture, CO2 incubators, bacterial

incubators, high-speed refrigerated centrifuges with rotors, refrigerated microfuges, gel

electrophoresis equipment and power supplies, orbital-shaking water baths, spectrophotometers and 

a luminometer, a monochromator-based multi-mode microplate reader for fluorescence and

luminescence, analytical balances; autoclaves and drying ovens, –20oC and –80oC freezers, fridges, 

liquid nitrogen storage tank and thermocyclers for PCR. For fluorescent microscopy and bright field 

microscopy a Nikon 80i epifluorescence microscope with a color digital camera equipped with the 

Elements software analysis package is available in the Dr. Rumbaugh’s lab. Additional equipment 

available in the Department of Microbiology and Immunology include an ABI7000 real time PCR

machine, a Typhoon phosphor-imager and and gel imaging equipment. Specific to this project, the 

SilhouetteStar laser scanning wound imaging, 3D measurement and documentation system, will be 

used to document wound area and volume. The SilhouetteStar is a shared resource in the

Department of Surgery. A Nikon TiE confocal microscope, which is equipped with an option known as 

N-STORM (Nikon Stochastic Optical Resolution Microscopy) is available in the Imaging Core and will 

be used for the described imaging studies. Dr. Rumbaugh’s laboratory also prepares their own tissue 

and slides for histopathology, using a Bright OTF5000 cryostat to produce thin, frozen tissue sections. 

CHRISTOPHER (TEXAS TECH UNIVERSITY)

AFM: Dr. Christopher has access to an Asylum Research MFP-3D Infinity AFM in the TTU Materials 

Characterization Research Center. This system has a 35nm resolution in the Z axis, and 150pm 

resolution in the XY plane. Its software allows easy setup so it can operate in tapping, forcedisplacement, and AM-FM modes for all the proposed measurements. Furthermore, the selfcalibration function allows precise and repeatable measurements. It is equipped to handle liquid 

environments as well. It can hold large samples (up to 80 mm in diameter). It will provide an ideal 

tool for the proposed measurements of the biofilm samples.

Confocal: Dr. Christopher has access to a 3i Marianas Spinning disk Confocal microscope in the 

TTU Materials Characterization Research Center. This tool allows sampling of large fields in a single 

image, unlike laser-scanning confocal microscopes. This results in fast image capture (1000 fps) and 

enables tracking of fluorescent particles, while maintaining high quantum efficiency. This allows its 

use in the microrheology application in the proposed work.

SHEAR (UNIVERSITY OF TEXAS AT AUSTIN)

Major equipment to be used for cell preparation and fluorescence microscopy currently resides within 

the Shear laboratory. This includes a Zeiss Axiovert fluorescence/DIC microscope outfitted with a 

scientific-grade fast low-noise readout CCD camera and cell-culturing facilities, including CO2- 

controlled incubators, sterile hood space, water baths, table-top centrifuges, and standard solution 

preparation facilities (balances, analytical balances, high-purity water dispenser, chemical 

hoodspace). Various micro-3D printing instruments exist in the Shear lab, comprising femtosecond 

titanium:sapphire laser systems, associated optics (including one- and two-axis raster scanning 

mirrors and digital micromirror device dynamic masks), and inverted microscope systems with highresolution vertical axis scanning capabilities.
Contact PD/PI: Gordon, Vernita

Page 18

Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

RESEARCH & RELATED Senior/Key Person Profile(Expanded)

OMB Number: 4040-0001

Expiration Date: 06/30/2016

PROFILE - Project Director/Principal Investigator

Prefix: First Name*: Vernita Middle Name Last Name*: Gordon Suffix: 

Position/Title*: Assistant Professor

Organization Name*: The University of Texas at Austin

Department: 

Division: 

Street1*: 

Street2: 

City*: 

County: 

State*: 

Province:

Country*:

Zip / Postal Code*:

Phone Number*: Fax Number:

E-Mail*:

Credential, e.g., agency login:

Project Role*: PD/PI Other Project Role Category:

Degree Type: Degree Year:

Attach Biographical Sketch*: File Name: Vernita_Gordon_Biosketch1027054133.pdf

Attach Current & Pending Support: File Name:
Contact PD/PI: Gordon, Vernita

Page 19

Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

PROFILE - Senior/Key Person

Prefix: First Name*: Kendra Middle Name Last Name*: Rumbaugh Suffix:

Position/Title*: Assistant Professor

Organization Name*: Texas Tech University Health Science Center

Department:

Division:

Street1*:

Street2:

City*:

County:

State*:

Province:

Country*:

Zip / Postal Code*:

Phone Number*: Fax Number:

E-Mail*:

Credential, e.g., agency login:

Project Role*: Other (Specify) Other Project Role Category: Collaborator

Degree Type: Degree Year:

Attach Biographical Sketch*: File Name: Kendra_Rumbaugh_Biosketch1027054136.pdf

Attach Current & Pending Support: File Name:

PROFILE - Senior/Key Person

Prefix: First Name*: Christopher Middle Name F Last Name*: Gordon Suffix:

Position/Title*: Assistant Professor

Organization Name*: Texas Tech University

Department:

Division:

Street1*:

Street2:

City*:

County:

State*:

Province:

Country*:

Zip / Postal Code*:

Phone Number*: Fax Number:

E-Mail*:

Credential, e.g., agency login:

Project Role*: Other (Specify) Other Project Role Category: Collaborator

Degree Type: Degree Year:

Attach Biographical Sketch*: File Name: Gordon_Christopher_Biosketch1027054299.pdf

Attach Current & Pending Support: File Name:
Contact PD/PI: Gordon, Vernita

Page 20

Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

PROFILE - Senior/Key Person

Prefix: Dr. First Name*: Jason Middle Name Last Name*: Shear Suffix: PhD

Position/Title*: Associate Professor, PhD 

Organization Name*: The University of Texas atAustin 

Department:

Division: 

Street1*: 

Street2: 

City*: 

County: 

State*: 

Province:

Country*:

Zip / Postal Code*:

Phone Number*: Fax Number:

E-Mail*:

Credential, e.g., agency login:

Project Role*: Other (Specify) Other Project Role Category: Collaborator

Degree Type: Degree Year:

Attach Biographical Sketch*: File Name: Shear_Biosketch 11_16_1027054297.pdf

Attach Current & Pending Support: File Name:
Contact PD/PI: Gordon, Vernita

Biosketches Page 21

1 

OMB No. 0925-0001/0002 (Rev. 08/12 Approved Through 8/31/2015)

BIOGRAPHICAL SKETCH

Provide the following information for the Senior/key personnel and other significant contributors.

Follow this format for each person. DO NOT EXCEED FIVE PAGES.

NAME: Gordon, Vernita Diane

eRA COMMONS USER NAME (credential, e.g., agency login): 

POSITION TITLE: Assistant Professor of Physics

EDUCATION/TRAINING (Begin with baccalaureate or other initial professional education, such as nursing, 

include postdoctoral training and residency training if applicable. Add/delete rows as necessary.)

DEGREE Completion 

(if Date FIELD OF STUDY INSTITUTION AND LOCATION applicable) MM/YYYY

Vanderbilt University, Nashville, TN B.S. 05/97 Physics and Math

Harvard University, Cambridge, MA A.M. 06/01 Physics 

Physics (experimental Harvard University, Cambridge, MA Ph.D. 11/03 soft condensed matter)

Physics of University of Edinburgh, Edinburgh, Scotland Postdoc 05/06 biomembranes

Biological physics of

University of Illinois, Urbana-Champaign, IL Postdoc 07/10 bacteria and

biomembranes

A. Personal Statement

We aim to determine what physical structures and mechanics develop in chronic wounds infected by 

Pseudomonas aeruginosa biofilms, and how spatial structure and mechanics contribute to virulence, antibiotic 

resistance, and resistance to phagocytic clearance by the immune system. For this, we will take a 

multidisciplinary approach that combines innovative techniques from physical science and from microbiology. 

This work is a good fit to my group’s expertise, since research currently based in my lab focuses on the 

mechanical and structural properties of single-cell and multicellular biological systems. My primary expertise 

lies in optical microscopy and quantitative image analysis of systems characterized by 1-100 μm lengthscales. 

My primary field of training is soft-matter physics and much of my microscopy work has focused on 

characterizing mechanics and sub-micron microstructure. More recently, I have acquired expertise in bacteria, 

specifically P. aeruginosa. After I began my faculty position I established another expertise in the spatial 

characterization and manipulation of dynamically developing systems of many bacteria. My lab can perform 

experiments combining mechanical, structural, and biological manipulation and measurement, a vanishingly 

rare ability. Thus, I am uniquely positioned to oversee the research described in this proposal. I have the 

experience and leadership to lead this project and to direct joint efforts with surgical, microbiological, 

engineering, and chemical collaborators as this project requires. This is substantiated by my track record of 

successful publication with medical and biological researchers. This includes a manuscript under review at 

mBio with Kendra Rumbaugh, who is a collaborator on this proposal.

I have New Investigator status; my Early Stage Investigator status ended in March 2015. I began my faculty 

position at UT Austin in 2010 and my tenure clock was stopped for the 2011-2012 and 2013-2014 academic 

years, so I have completed four years on the tenure clock.

Publications most-closely related to the present proposal: 

1.
Contact PD/PI: Gordon, Vernita

Biosketches Page 22

2 

2. Role of multicellular aggregates in biofilm formation. Kragh, K., J. Hutchison, G. Melaugh, C. Rodesney,

A. Roberts, Y. Irie, P. Jensen, S. Diggle, R. Allen*, V. Gordon*, and T. Bjarnsholt*. mBio, 2016. 7: p. 

e00237-16 * = joint corresponding authors

3. Tobramycin and bicarbonate synergise to kill planktonic Pseudomonas aeruginosa, but antagonise to 

promote biofilm survival. Kaushik, K., J. Stolhandske, O. Shindell, H. Smyth, and V. Gordon. npj 

Biofilms and Microbiomes, 2016. 2: p. 16006

4. Single-Cell Control of Initial Spatial Structure in Biofilm Development Using Laser Trapping. Hutchison, 

J., C. Rodesney, K. Kaushik, H. Le, D. Hurwitz, Y. Irie, and V. Gordon. Langmuir, 2014. 30: p. 4522– 

4530

B. Positions and Honors

Positions and Employment

2010- Assistant Professor, Department of Physics, University of Texas at Austin

Other Experience and Professional Memberships

2007-present American Physical Society (APS)

2016-2020Secretary/Treasurer for the Division of Biological Physics of the APS 

2009-2010; 2012-present American Society for Microbiology

Symposium convener for the 2016 Microbe meeting.

2014- Society of Rheology

2015- Biophysical Society

2013- NSF grant proposal reviewer

2014 Instructor, Hands-On Research in Complex Systems School, International Center for

Theoretical Physics , Trieste, Italy.

Honors

1995-1997 William and Nancy McMinn Honor Scholarship in Physics, Vanderbilt University 

2008-2010 Postdoctoral Fellow, Cystic Fibrosis Foundation

2012 Contributed abstract selected for talk at the American Society for Microbiology annual meeting 

2012 Invited poster presentation, Human Frontiers Science Project annual meeting

2013 Hyer Research Award, Texas Section of the American Physical Society

For the best research done by a 2-person team of a faculty member and an undergraduate.

Invited Talks (since joining UT Austin faculty in 2010)

2011 National Society of Black and Hispanic Physicists annual meeting, Austin, TX 

Physics Department Seminar, Trinity College, San Antonio, TX

2012 Workshop on Biomembranes, Kavli Institute of Theoretical Physics – China, Beijing, China 

Center for Theoretical Biology Seminar, Beijing University, Beijing, China

2013 Physics and Biology Departments joint seminar, Austin College, Sherman, TX 

Holliday Lecture (named Physics colloquium), Vanderbilt University, Nashville, TN

2014 Biophysics Seminar, Center for Theoretical Biological Physics, Rice University, Houston, TX 

Condensed Matter Physics Seminar, University of Edinburgh, Edinburgh, United Kingdom 

Chemistry Seminar, University of Leeds, Leeds, United Kingdom

Physics Seminar, Texas Christian University, Fort Worth, TX

2015 Mechanical Engineering Seminar, Dept. of Mechanical Engineering, Texas Tech, Lubbock, TX 

Biomedical Engineering Seminar, Dept. of Biomedical Engineering, UT Brownsville, Brownsville, TX 

Soft Matter Seminar, Soft Matter Institute, Dept. of Physics, Georgetown University, Washington DC 

Center for Biofilm Engineering (CBE) Seminar, CBE, Montana State University, Bozeman, MT 

Biophysics Colloquium, Cornell University, Ithaca, NY
Contact PD/PI: Gordon, Vernita

Biosketches Page 23

3 

Physics Colloquium, Emory University, Atlanta, GA

Biophysics Seminar, Massachusetts Institute of Technology, Cambridge, MA 

New England Complex Fluids Meeting, Harvard University, Cambridge, MA

2016 March Meeting of the American Physical Society, Baltimore, MD

Colloquium, Dept. of Physics, University of Massachusetts – Amherst, Amherst, MA 

Colloquium, Dept. of Physics, Trinity University, San Antonio, TX

Center for Bioengineering Seminar, University of Californa – Santa Barbara, Santa Barbara, CA 

American Society of Microbiology Microbe 2016 annual meeting, Boston, MA

Texas Soft Matter meeting, Dallas, TX

American Chemical Society National Meeting, Philadelphia, PA

Seminar, Chemical Engineering, University of Pennsylvania, Philadelphia, PA 

Biosoft Seminar, Dept. of Physics, Georgia Institute of Technology, Atlanta, GA 

Colloquium, Chemical Engineering, Stanford University, Stanford, CA 

Biophysics Seminar, Dept. of Physics, University of California – Irvine, Irvine, CA 

American Chemical Society Southwest Regional Meeting, Galveston, TX 

Biophysics Seminar, Dept. of Physics, Princeton University, Princeton, NJ

Soft Matter Seminar, Dept. of Chemistry, Columbia University, New York, NY 

2017 Systems Biology Seminar, Bioinformatics Program, Boston University, Boston, MA

C. Contribution to Science

1. A major theme in my lab is understanding how spatial structure develops in multicellular bacterial 

systems such as biofilms, and how spatial structure impacts the biological responses of the bacteria, 

such as growth. Examples of bacterial processes that could lead to structure include aggregative 

tendencies, chemotaxis of motile bacteria, and growth instabilities.

1. Singly flagellated Pseudomonas aeruginosa chemotaxes efficiently by unbiased motor 

regulation. Cai Q, Li Z, Ouyang Q, Luo C, Gordon VD. 2016. mBio 7(2):e00013-16. 

doi:10.1128/mBio.00013-16.

This paper received a one-star recommendation from Faculty of 1000. 

2. Role of multicellular aggregates in biofilm formation. Kragh KN, Hutchison JB, Melaugh G, 

Rodesney C, Roberts AEL, Irie Y, Jensen PO, Diggle SP, Allen RJ*, Gordon V*, Bjarnsholt T*.* 

= joint corresponding authorship. 2016. mBio 7(2):e00237-16. doi:10.1128/mBio.00237-16

This paper received a two-star recommendation from Faculty of 1000. 

3. Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates. Melaugh G, 

Hutchison J, Kragh KN, Irie Y, Roberts A, Bjarnsholt T, V. D. Gordon, RJ Allen. (2016) PLoS 

ONE 11(3): e0149683. doi:10.1371/journal.pone.0149683

4. Single-cell control of initial spatial structure in biofilm development using laser trapping. J. B. 

Hutchison, C. A. Rodesney, K. S. Kaushik, H. H. Le, D. A. Hurwitz, Y. Irie, V. D. Gordon. 2014 

Langmuir 30:4522-4530 

This work was featured in

“Laser trapping to show the effects of bacterial arrangement on biofilm infection” 2014 

SPIE Newsroom, DOI:10.1117/2.1201412.005727

and in “’Laser Trapping’ technique could lead to better management of bacterial 

infections in CF patients” 2015 Cystic Fibrosis News Today

2. In bacterial biofilms, structure and mechanics are intimately connected, because the same 

extracellular polymers (EPS) that make up the biofilm matrix also control the biofilm’s viscoelastic 

mechanics. A single strain of biofilm-forming bacteria can produce more than one type of EPS 

molecule – for example P. aeruginosa makes Psl, Pel, and alginate. Another major theme in my lab is 

understanding how different types of EPS materials impact the mechanics of biofilms and of single 

bacteria.

1.
Contact PD/PI: Gordon, Vernita

Biosketches Page 24

4 

2. Asymmetry and inequity in the inheritance of a bacterial adhesive. Benjamin J Cooley, Sheri 

Dellos-Nolan, Numa Dhamani, Ross Todd, William Waller, Daniel Wozniak and Vernita D 

Gordon. 2016. doi: 10.1088/1367-2630/18/4/045019

3. The extracellular polysaccharide Pel makes the attachment of P. aeruginosa to surfaces 

symmetric and short-ranged. B.J. Cooley, T.W. Thatcher, S.M. Hashmi, G. L’Her, H.H. Le, D.A.

Hurwitz, D. Provenzano, A. Touhami, V.D. Gordon. 2013 Soft Matter 9:3871-3876

3. To find new approaches to antibiotic treatment that combine standard antimicrobials with spatial 

properties of a multicellular bacterial system, we use the opportunistic human pathogen Pseudomonas 

aeruginosa and the aminoglycoside antibiotic tobramycin. I have studied this as a postdoc and a PI.

1. Tobramycin and bicarbonate synergise to kill planktonic Pseudomonas aeruginosa, but 

antagonise to promote biofilm growth. Karishma S Kaushik, Jake Stolhandske, Orrin Shindell, 

Hugh D Smyth and Vernita D. Gordon. npj Biofilms and Microbiomes (2016) 2, 16006; 

doi:10.1038/npjbiofilms.2016.6

2. A low-cost, hands-on module to characterize antimicrobial compounds using an 

interdisciplinary, biophysical approach. K.S. Kaushik, A. Kessel, N. Ratnayeke, V.D. Gordon. 

2015 PLoS Biology, DOI:10.1371/journal.pbio.1002044

3. The spatial profiles and metabolic capabilities of microbial populations impact the growth of 

antibiotic-resistant mutants. K.S. Kaushik, N. Ratnayeke, P. Katira, V.D. Gordon. 2015 Journal 

of the Royal Society Interface 12:20150018

4. The PEL polysaccharide can serve a structural and protective role in the biofilm matrix of 

Pseudomonas aeruginosa. Colvin, K. M., Gordon, V. D., Murakami, K., Wozniak, D. J., Wong,

G. C. L., Parsek, M. R. 2011 PLOS Pathogens 7:e1001264

4. The site of adhesion of a cell to another cell, an extracellular matrix, or an antimicrobial peptide is 

frequently associated with the formation of heterogeneities and topological changes in the membrane. 

I have studied this as a postdoc and a PI.

1. Specific adhesion of membranes simultaneously supports dual heterogeneities in lipids and 

proteins. O. Shindell, N. Mica, M. Ritzner and V. D. Gordon. 2015 Physical Chemistry 

Chemical Physics 17:15598-15607 DOI: 10.1039/c4cp05877a

2. Mechanism of a prototypical synthetic membrane-active antimicrobial: Efficient hole-punching 

by targeting lipids with negative spontaneous curvature. L. Yang, V. D. Gordon, D. R. Trinkle,

M. A. Davis, C. DeVries, A. Som, J. E. Cronan, Jr., G. N. Tew, G. C. L. Wong. 2008 

Proceedings of the National Academy of Sciences of the USA 105:20595-20600

3. Adhesion promotes phase separation in mixed-lipid membranes. V. D. Gordon, M. Deserno, S.

U. Egelhaaf, W. C. K. Poon. 2008 Europhysics Letters 84:48003

4. Synthetic antimicrobial oligomers induce composition-dependent topological transition in 

membranes. L. Yang, V. D. Gordon, A. Mishra, A. Som, K. Purdy, M. A. Davis, G. N. Tew, and

G. C. L. Wong. 2007 Journal of the American Chemical Society 129:12141-12147

Complete List of Published Work in MyBibliography: 

http://www.ncbi.nlm.nih.gov/sites/myncbi/1vqypcpindo5i/bibliography/47369830/public/?sort=date&dir

ection=ascending

D. Research Support

Ongoing
Contact PD/PI: Gordon, Vernita

Biosketches Page 25

5

Completed

National Science Foundation (PI: Touhami; Gordon is co-PI) 9/1/13-8/31/15 

MRI: Acquisition of an Integrated Fluorescence and Atomic Force Microscope for Biophysical and Biomedical 

Research and Education

This funding has been used to acquire and install a microscope with integrated epifluorescence imaging and 

atomic force microscopy.
Contact PD/PI: Gordon, Vernita

Biosketches Page 26

OMB No. 0925-0001/0002 (Rev. 08/12 Approved Through 8/31/2015)

BIOGRAPHICAL SKETCH

Provide the following information for the Senior/key personnel and other significant contributors.

Follow this format for each person. DO NOT EXCEED FIVE PAGES.

NAME: Kendra P. Rumbaugh

eRA COMMONS USER NAME (credential, e.g., agency login): 

POSITION TITLE: Associate Professor

EDUCATION/TRAINING (Begin with baccalaureate or other initial professional education, such as nursing, 

include postdoctoral training and residency training if applicable. Add/delete rows as necessary.)

INSTITUTION AND LOCATION

DEGREE

(if 

applicable)

Completion 

Date 

MM/YYYY

FIELD OF STUDY

University of Texas at El Paso B.S. 1993-1996 Microbiology

Texas Tech University Health Sciences Center 

(TTUHSC) Ph.D. 1996-2001 Medical Microbiology

University of California at San Francisco (UCSF) Post-doc 2001-2002 Microbial Pathogenesis

A. Personal Statement

The research in my laboratory is focused on bacterial pathogenesis in acute and chronic wound and soft tissue 

infections. We have over 16 years’ experience investigating bacterial pathogenesis utilizing rodent wound 

models, and our group has made seminal contributions towards our understanding of the roles quorum sensing 

and biofilms play in vivo. My laboratory also has expertise in investigating how polymicrobial interactions and 

bacterial biofilms affect pathogenesis and modulate innate immune responses in the local wound environment. 

We have performed numerous efficacy studies of antimicrobial and antibiofilm compounds for academic 

collaborators and private companies, the data for which have been used to justify Phase II clinical trials. I have 

sat on wound infection-related study sections for a number of organizations including the American Diabetes 

Association, the Department of Defense, NIH and VA. Thus, I am extremely familiar with the most current 

advances in the field. As a principal investigator I have successfully administered several wound infectionrelated basic science, translational, and clinical projects. I have also participated in many long-term, productive 

collaborations. Most notable, for the past 6 years my group has worked closely with Dr. Marvin Whiteley’s 

laboratory to advance our understanding of how polymicrobial interactions affect microbial metabolism and 

pathogenesis in vivo by combining their cutting-edge genomic approaches with our animal models. Thus, we 

have all the necessary reagents, animal models, and productive collaborative relationships already in place to 

make us extremely well-suited to complete this new project in collaboration with Dr. Gordon.

B. Positions and Honors

Positions and Employment

2001-2002 Postdoctoral Research Fellow, UCSF, Dept. of Anesthesia and Preoperative Care, San

Francisco, CA (mentor, Jeanine Wiener-Kronish)

2002-2003 Postdoctoral Research Fellow, TTUHSC, Dept. of Surgery, Lubbock, TX 

2003-2004 Instructor, Department of Surgery, TTUHSC, Lubbock, TX

2004-2005 Research Assistant Professor, Department of Surgery, TTUHSC, Lubbock, TX 

2006-2012 Assistant Professor, Department of Surgery

2012-present Associate Professor Department of Surgery, with joint appointments in Department of 

Cell Biology and Biochemistry and Microbiology and Immunology, TTUHSC, Lubbock, 

TX
Contact PD/PI: Gordon, Vernita

Biosketches Page 27

Other relevant experience and professional associations

2004 Ad hoc member NIH ‘Host Interactions with Bacterial Pathogens’ (HIBP) Study Section 

2008 Ad hoc member Department of Defense, War Supplement

2008-present Association for Women in Science (West-Texas chapter co-founder and previous 

President)

2009 Ad hoc member Defense Medical Research and Development Program (DMRDP) 

2009-2014 American Diabetes Association Research Grant Review Committee

2011-2013 American Society for Microbiology (Texas Branch President-elect) 

2012 Ad hoc member NIAID Investigator Initiated Program Projects (P01) 

2012 Reviewer US Army Medical Research and Materiel Command

2012-present Editorial board, FEMS Microbiology Letters

2013 Reviewer US Army Combat Casualty Care Research Program (CCCRP) 

2013-present American Society for Microbiology (Texas Branch President)

2013-present Ad hoc member NIAID “Anti-Infective Therapeutics” Special Emphasis Panel ZRG1 IDM10

2013-present Panel member, Department of Veterans Affairs Veterans Health Administration Office of 

Research and Development (Infectious Disease B (INFB)) 

2014 Ad hoc member NIAID AREA (R15) ZRG1 IDM S (81)

2015, 2016 Ad hoc member Congressionally Directed Medical Research Programs (CDMRP) and 

Military Infectious Diseases Research Program (MIDRP)

2016 Ad hoc member NIH ZRG1 Musculoskeletal, Oral and Skin Sciences (MOSS) T02 

Special Emphasis Panel

2016 Ad hoc reviewer Wellcome Trust/ DBT India Alliance

2016 Panel Chair-Defense Medical Research and Development Program (DMRDP), Joint 

Program Committee (6)- Burns, Wounds and Fractures

Honors and Awards

2004 Review of published work in ASM magazine “Microbe”, Current Topics Section 

2006 Review of published work in ASM magazine “Microbe”, Current Topics Section 

2006 TTUHSC President’s Young Investigator Award Recipient

2007, 2006, 2004 Cover Photos: J Bacteriol April 04, Appl Environ Microbiol July 06, Infect Immun Aug 07 

2009 Outstanding Faculty Mentor, Texas Tech Univ. & Howard Hughes Medical Institute 

2009 Paper included in the ‘Editor’s Choice’ section of Science (Vol 323)- March ed. 

2009 Review of published work in ASM magazine “Microbe”, Journal Highlights 

2009 Work discussed in News Feature “Tinker, Bacteria, Eukaryote, Spy” Nature

(Vol 459)

2014 Outstanding Faculty Teaching Award (from TTUHSC Student Government) 

2014 Susan G. Talkmitt Science Motivator Award (from TTU)

C. Contributions to Science

1. My early work as a graduate student and postdoctoral fellow focused on understanding the pathogenesis of 

Pseudomonas aeruginosa during infection. In particular I was interested in how P. aeruginosa used quorum 

sensing (a relatively new term at the time) to control its virulence. As a graduate student, I was the first to 

show that knocking out quorum sensing genes significantly impaired P. aeruginosa virulence in a murine 

burn wound model, results that were subsequently confirmed by several other groups in several other 

models of infection. When I started my own laboratory group my interest in P. aeruginosa quorum sensing 

evolved into understanding how the small chemical signals (autoinducers) made by bacteria affected host 

cells in a process called ‘interkingdom signaling’. Our seminal contributions in this area (selected papers 

chronologically listed below) provided mechanistic information about how quorum signals induced apoptosis 

and inflammation in host cells. Several of these studies were highlighted in Microbe, Science and Nature. 
Contact PD/PI: Gordon, Vernita

Biosketches Page 28

a. Williams, S.C. Patterson, E. K., Carty, N.L., Griswold, J. A., Hamood, A. N. and Rumbaugh, K.P. 

2004. Pseudomonas aeruginosa Autoinducer Enters and Functions in Mammalian Cells. J. Bacteriol. 

186(8): 2281-7. PMID:15060029 Cover photo

b. Beale, E., Li, G., Tan, M.W., Rumbaugh, K.P. 2006. Caenorhabditis elegans Senses Bacterial 

Autoinducers. Appl Environ Microbiol. 72(7):5135-7. PMID:16820523 Cover photo (recommended by 

F1000)

c. Shiner, E.K., Terentyev, D., Bryan, A., Sennoune, S., Martinez-Zaguilan, R., Li, G., Gyorke, S., 

Williams, S.C. and Rumbaugh, K.P. 2006. Pseudomonas aeruginosa Autoinducer Modulates Host 

Cell Responses through Calcium Signaling. Cellular Microbiol. 8(10):1601-10. PMID:16984415

d. Jahoor A., Patel R., Bryan, A., Do C., Krier J., Watters C., Wahli W., Li, G., Williams S.C., Rumbaugh

K.P. 2008. Peroxisome Proliferator Activated Receptors Mediate Host Cell Pro-inflammatory 

Responses to P. aeruginosa Autoinducer. J Bacteriol. Jul;190(13):4408-15. Epub 2008 Jan 4. 

PMID:18178738

2. My laboratory has also had a long time interest in role of bacterial biofilms in wound infections, healing 

dynamics and antimicrobial tolerance. We have developed a murine chronic wound model to study how 

biofilms impair healing and other host tissue processes and how the host environment modulates biofilm 

formation. One major area of focus has been to determine how the diabetic environment influences biofilm 

processes.

a. Rumbaugh, K. P. and Carty, N. L. 2010. In vivo models of biofilm infection. In: Biofilm Infections. 

Bjarnsholt, Jensen, Østrup, Høiby (Eds.). Springer, New York, NY. ISBN:978-1-4419-6083-2 

b. Watters C., Deleon K., Trivedi U., Griswold J.A., Lyte M., Hampel K.J., Wargo M.J., Rumbaugh K.P. 

2013. Pseudomonas aeruginosa biofilms perturb wound resolution and antibiotic tolerance in diabetic 

mice. Med Med Microbiol Immunol. 2013 Apr;202(2):131-41. (recommended by F1000)

c. Watters C, Everett JA, Haley C, Clinton A, Rumbaugh KP. Insulin Treatment Modulates the Host 

Immune System To Enhance Pseudomonas aeruginosa Wound Biofilms. Infect Immun. 2014 

Jan;82(1):92-100.

d. Trivedi U, Parameswaran S, Armstrong A, Burgueno-Vega D, Griswold J, Dissanaike S, Rumbaugh 

KP. Prevalence of Multiple Antibiotic Resistant Infections in Diabetic versus Nondiabetic Wounds. J 

Pathog. 2014;2014:173053. PMID: 25054067

3. Utilizing our animal models of infection we have collaborated on several translational projects tounderstand 

the clinical consequences of biofilms in wounds. Several of these projects involved working with small 

companies on Phase I Pre-clinical trials.

a. DeLeon, K., Watters, C., Baldin, F., Hamood, A., Griswold, J., Sreedharan, S., and Rumbaugh, K.P. 

2009. Efficacy of gallium maltolate in treating Pseudomonas aeruginosa infection in a thermally-injured 

mouse model. Antimicrob Agents Chemother. Apr; 53(4):1331-1337. PMID:19188381

b. Wolcott, R.D., Rumbaugh, K. P., James, G., Schultz, G., Phillips, P., Yang, Q., Watters, C., Stewart, P.

S. and Dowd, S. E. 2010. Biofilm maturity studies indicate sharp debridement opens a time-dependent 

therapeutic window. J Wound Care 19(8) 320-328. PMID:20852503 (recommended by F1000)

c. Gawande PV, Clinton AP, LoVetri K, Yakandawala N, Rumbaugh KP, Madhyastha S. Antibiofilm 

Efficacy of DispersinB® Wound Spray Used in Combination with a Silver Wound Dressing.

Microbiology Insights 2014:7, 9-13. PMID: 24826078

d. Rai A, Pinto S, Velho TR, Ferreira AF, Moita C, Trivedi U, Evangelista M, Comune M, Rumbaugh KP, 

Simões PN, Moita L, Ferreira L. One-step synthesis of high-density peptide-conjugated gold 

nanoparticles with antimicrobial efficacy in a systemic infection model. Biomaterials. 2016; 85:99-110.

4. Chronic wound infections tend to be polymicrobial, so much of my more current work has focused on 

studying the interspecies interactions occurring in wound infections. Many of these studies have focused on 

the two most prominent bacterial species found in chronic wounds, P. aeruginosa and S. aureus. 

Independently, and in collaboration with Marvin Whiteley’s group we have uncovered new and important 

mechanisms of interaction between these two pathogens that influence infection.
Contact PD/PI: Gordon, Vernita

Biosketches Page 29

a. Dalton, T., Dowd, S. E., Wolcott, R.D., Sun, Y., Watters, C., Griswold, J.A. and Rumbaugh, K.P. 2011. 

An in vivo polymicrobial biofilm wound infection model to study interspecies interactions. PLoS One. 

2011;6(11):e27317. Epub 2011 Nov 4. PMID:22076151

b. Korgaonkar , U. Trivedi , K.P. Rumbaugh , M. Whiteley. 2013. Community surveillance enhances P. 

aeruginosa virulence during polymicrobial infection. Proc Natl Acad Sci U S A. 2013 Jan 

15;110(3):1059-64. PMID:23277552

c. DeLeon S, Clinton A, Fowler H, Everett J, Horswill AR, Rumbaugh KP. Synergistic Interactions of 

Pseudomonas aeruginosa and Staphylococcus aureus in an In Vitro Wound Model. Infect Immun. 2014 

Aug 25. pii: IAI.02198-14. PMID:25156721

d. Gabrilska R and Rumbaugh KP. Biofilm Models of Polymicrobial Infection. Future Microbiol. 2015. 

Dec;10:1997-2015. PMID:26592098

5. For the past 6 years my group has worked closely with Dr. Marvin Whiteley’s laboratory to advance our 

understanding of how polymicrobial interactions affect microbial metabolism and pathogenesis in vivo by 

combining their cutting-edge genomic approaches with our animal models. One major focus of this work has 

been on the interspecies interactions among oral pathogens. For these studies we developed a murine 

abscess model to study polymicrobial infection and optimized techniques such as RNAseq and Tnseq to 

uncover new mechanisms of bacterial synergy that promote infection.

a. Ramsey, M.C., Rumbaugh, K.P. and Whiteley, M. Metabolic cross-feeding enhances virulence in a 

model polymicrobial infection. PLoS Pathogens 2011 Mar;7(3):e1002012. Epub 2011 Mar 31. 

PMID:21483753 (recommended by F1000)

b. Jorth P, Trivedi U, Rumbaugh K, Whiteley M. Probing bacterial metabolism during infection using highresolution transcriptomics. J Bacteriol. 2013 Nov;195(22):4991-8. [Epub ahead of print]. 

PMID:23974023. Chosen for special Commentary (23974023)

c. Stacy A, Everett J, Jorth P, Trivedi U, Rumbaugh KP, Whiteley M. Bacterial fight-and-flight responses 

enhance virulence in a polymicrobial infection. Proc Natl Acad Sci U S A. 2014 May 13. pii: 201400586. 

[Epub ahead of print]. PMID: 24825893

d. Turner KH, Everett J, Trivedi U, Rumbaugh KP, Whiteley M. Requirements for Pseudomonas 

aeruginosa Acute Burn and Chronic Surgical Wound Infection. PLoS Genet. 2014 Jul 

24;10(7):e1004518. PMID: 25057820

Complete List of Published Work in MyBibliography:

http://www.ncbi.nlm.nih.gov/sites/myncbi/kendra.rumbaugh.1/bibliography/47366413/public/?sort=date&directi

on=ascending

D. Research Support

Ongoing

NIH/R01 (Rumbaugh, Sub-contract PI; Whiteley, PI) 2016-2020 

(total subcontract)

“Mechanisms of Pseudomonas aeruginosa viruence in polymicrobial wound infections”

The overall goal of this research plan is to determine how interactions between Pseudomonas aeruginosa and 

other microbes that commonly co-infect wounds impact wound severity. To accomplish this goal, in vivo murine 

wound models and high-throughput genomics techniques will be employed to identify and characterize 

microbial genes required for enhanced pathogenesis during co-infection.

NIH/NIAID R15AI105763 (Rumbaugh, PI) 2014-2017

“Pseudomonas aeruginosa and Staphylococcus aureus Interspecies Interactions in Wounds”

The goals of this study are to 1) characterize P. aeruginosa and S. aureus interspecies interactions in an in 

vitro wound environment; 2) determine how components of the wound environment inhibit P. aeruginosa's 

ability to kill S. aureus and thus promote stable coinfections; and 3) investigate what consequences P. 

aeruginosa/S. aureus coinfection has on wound resolution in vivo. 

Army Research Office grant 62507-LS (Rumbaugh, Sub-contract PI;Whiteley, PI) 2013-2017
Contact PD/PI: Gordon, Vernita

Biosketches Page 30

“Polymicrobial virulence mechanisms in chronic wounds”

The overall objective of this project is to study peptidoglycan-mediated interactions between P. aeruginosa and

S. aureus or Acinetobacter baumannii in a murine chronic wound model, primarily using RNAseq technology.

Completed

NIH/NIAID R21AI107570 (Rumbaugh, Sub-contract PI; Whiteley, PI) 2014-2016 

“Genetic determinants of bacterial fitness in polymicrobial wound infections”

The overall goal of this research plan is to examine, from a genomic standpoint, how interactions between 

opportunistic pathogens impact in vivo persistence in acute and chronic wound infections. To accomplish this goal, 

high-throughput genomics techniques will be employed to identify microbial genes that are required for and 

expressed during polymicrobial synergy.

NIH/NIDCR R01DE020100 (Rumbaugh, Sub-contract PI; Whiteley, PI) 2011-2015 

“Metabolite sensing in an oral polymicrobial community”

The major goals of this project are to define the interspecies relationships between the oral pathogens A. 

actinomycetemcomitans and S. gordonii.
Contact PD/PI: Gordon, Vernita

Biosketches Page 31

BIOGRAPHICAL SKETCH

NAME POSITION TITLE

Christopher, Gordon F. Assistant Professor of Mechanical Engineering

eRA COMMONS USER NAME (credential, e.g., agency login)

EDUCATION/TRAINING (Begin with baccalaureate or other initial professional education, such as nursing, include postdoctoral training and 

residency training if applicable.)

DEGREE INSTITUTION AND LOCATION MM/YY FIELD OF STUDY (if applicable)

Columbia University (New York, NY) BS 5/02 Mechanical Engineering

Columbia University (New York, NY) BA 5/03 Film

Carnegie Mellon University (Pittsburgh, PA) MS 5/04 Mechanical Engineering

Carnegie Mellon University (Pittsburgh, PA) MS 5/08 Chemical Engineering

Carnegie Mellon University (Pittsburgh, PA) PhD 5/08 Mechanical Engineering

Rheology and Complex National Institute of Standards and Technology Post Doc 1/10 Fluids

A. Personal Statement

The goal of the proposed research is to characterize the physio-chemical properties of wound biofilms both invivo and ex-vivo. I have a strong background in mechanical and chemical engineering, with a research focus 

on the rheology of complex fluids and interfaces. During my Ph.D. in mechanical engineering from Carnegie 

Mellon University under the guidance of Prof. Shelley Anna, I worked extensively in the characterization of 

complex fluids and their use in microfluidics using both shear and extensional rheology. During my post 

doctoral work as an NRC fellow at NIST, I continued to develop skills in the modeling and characterizing of 

complex fluids, development of novel microrheology techniques, and in the use and fabrication of MEMS 

devices. My lab at TTU focuses on the development of novel rheology techniques to examine the effects of 

confinement on soft matter/complex fluids and methods to study interfacial rheology. We have focused on a 

wide range of problems including bulk protein solution rheology, interfacial rheology of proteins solutions, and 

the interfacial rheology of biofilms at air/water interfaces. We have developed skills in handling and 

characterizing biomaterials in our lab, and are well versed in a wide range of material characterization 

techniques including bulk, interfacial, and micro rheology. Based on my work and record, I have received 

several NSF grants in the areas of rheology and biomaterials.

1. Zhang, Z. and G.F. Christopher, “Effect of particulate contaminates on the development of biofilms at air/water 

interfaces.” Langmuir, 2016. 32 (11) p. 2724-2730.

B. Positions and Honors

Positions and Employment

2009-2010 National Institute of Standards and Technology, NRC Postdoctoral Fellow 

2010- Texas Tech University Department of Mechanical Engineering, Assistant Professor

Other Experience and Professional Memberships

2004- Member, Society of Rheology

2008- Reviewer for Scholarly Journal: Journal of Applied Polymer Science, Journal of

Rheology, Microfluids and Nanofluids

2010- Member, American Institute of Chemical Engineers

2011 Panel Reviewer, NSF Particulate and Multiphase Flow
Contact PD/PI: Gordon, Vernita

Biosketches Page 32

Honors

2002 Magna Cum Laude, Columbia University, New York, NY

2005 DOWD ICES Fellow, Carnegie Mellon University, Pittsburgh,

2009 NIST Exploratory Research Grant, Gaithersburg, MD

2012 Sandia National Labsortories MEMS Design Competition, Texas Tech University, 

Lubbock, TX

C. Contributions to Science

Role of particle behavior on interfacial rheology of particle laden interfaces

Using advanced rheology and microscopy technquies developed in my lab, I have studied how changing

the properties of an interface effect the individual behavior, collective microstructure, and interfacial 

rheology of particle laden interfaces. The work is supported by 2 separate NSF grants, and has been 

widely cited in publications.

1. Supakar, T., Moradiafrapoli, M. Christopher, G. F., and J. Marston. “Spreading, encapsulation and transition to 

arrested shapes during drop impact onto hydrophobic powders.” Journal of Colloid and Interface Science, 2016. 

468 p.10-20

2. Barman, S. and G.F. Christopher, “Role of Capillarity and Microstructure on Interfacial Viscoelasticity of Particle 

Laden Interfaces.” Journal of Rheology, 2015. 60 (1) p. 35-45.

3. Snoeyink, C., Barman, S., and G.F. Christopher, “Contact Angle Distribution at Fluid Interfaces.” Langmuir, 

2014. 31(3), p891-897.

4. Barman, S. and G Christopher, “Simultaneous Interfacial Rheology and Visualization of Densly Packed 

Aggregated Particle Laden Interfaces.” Langmuir, 2014. 30 (32), p. 9752-8760.

Interfacial Behavior of Biological Materials

We have done a number of studies focusing on how interfacial properties are affected by biomaterials. 

This work has primarily focused on 2 systems:1) how do globular proteins on and interface change 

interfacial viscoelasticity, and 2) how can a liquid interface be modified to disrupt the growth of pellicles. 

We have several publications in this area, and are supported by a NSF grant.

2. Zhang, Z. and G.F. Christopher, “Effect of particulate contaminates on the development of biofilms at air/water 

interfaces.” Langmuir, 2016. 32 (11) p. 2724-2730.

3. Zhang, Z and G.F. Christopher, “The nonlinear viscoelasticity of hyaluronic acid and its role in jointluibrication.” 

Soft Matter, 2014. 11(13), p.2596-2603.

4. Zhang, Z., Barman, S., and G.F. Christopher, “The Role of Protein Content on The Steady and Oscillatory 

Shear Rehology of Model Synovial Fluids.” Soft Matter, 2014. 10 (32), p. 5965-5973.

5. Zhang, Z., Barman, S., and G.F. Christopher, “Effect of Interfacial Viscoelasticity on the Bulk LinearViscoelastic 

Moduli of Globular Protein Solutions.” Physical Review E, 2014 89(5): p. 052306-052310

Elastic instabilities in microfluidics

Using microfluidic channels, we have examined how viscoelastic Mach number is a useful tool in 

characterizing purely elastic instabilities around microfluidic cylinders. In this work we have discovered a 

new class of flow instabilities around cylinders that had been previously un-reported. This work was 

supported by the American Chemical Society, and resulted in several well received publications

1. Shi, X. and G.F. Christopher, “Growth of Elastic Instabilities around Linear Arrays.” Physics of Fluids, 

Submitted.

2. Shi, X. and G.F. Christopher, “Mechanisms of Onset for Moderate Mach Number Instabilities ofViscoelastic 

Flows around Confined Cylinders.” Rheologica Acta, 2015. 54 (9-10), p.805-815.

3. Kenney, S., K. Poper, G. Chapagain, and G.F. Christopher, “Large Deborah number flows around confined 

microfluidic cylinders.” Rheologica Acta, 2013. 52(5): p. 485-497.

Droplet behavior in microfluidics
Contact PD/PI: Gordon, Vernita

Biosketches Page 33

During my PhD, I published several influential papers on the behavior of droplets in microfluidic channels 

detailing their generation, deformation, and coalescence.

Lin, Y., Barman, S., Christopher, G.F., S.L. Biswal, “In situ Microstructure Visualization and Interfacial Shear 

Rheology of Asphaltenes at Air/Oil-Water Interfaces.” Journal of Rheology, Submitted.

1. Christopher, G F and Anna, S L “Passive breakup of viscoelastic droplets and filament self-thinning at a 

microfluidic T-junction.” Journal of Rheology. 2009. 53 (3): p 663-683

2. Christopher, G F, Bergstein, J, et al. “Coalescence and splitting of confined droplets at microfluidic junctions.”

Lab on a Chip 2009. 8 (9): p1102-1109

3. Christopher, G F, Noharuddin N, et al. “Experimental observations of the squeezing-to dripping transition in Tshaped microfluidic junctions.” Physical Review E, 2008.78 (3) *

4. Christopher, G F and Anna, S L “Microfluidic methods for generating continuous droplet streams.” Journal of 

Physics D: Applied Physics, 2007.40 (19):p R319-R336

URL to complete list of published work: https://scholar.google.com/citations?user=sPQ48d4AAAAJ&hl=en

D. Research Support

Current Research Support

Using Active Materials at Liquid Interfaces to Regulate Bacterial Biofilm Mechanical Properties 

National Science Foundation

Role: PI

Dates 9/1/2016-8/31/2019

Description: The goal of this project is to understand how surface active materials can be used to disrupt the 

growth of a biofilm at an air/water interface.

Characterization of the Dynamic Behavior of Particle Contact Angle at an Oil/Water Interface

National Science Foundation

Role:co-PI

Dates 9/1/2016-8/31/2019

Description: The goal of this project is to characterize the dynamics of particles at an oil/water interface by 

measuring changes in three phase contact line and contact angle.

Testing Special Additive Manufacturing (AM) Materials Project

DOE/Consolidated Nuclear Security, LLC-PANTEX

Role: co-PI

Dates 3/10/2016-12/31/2017

Description: The goal of this project is to develop a 3D printer capable of printing high binder loading pastes 

for weapons manufacture.

Role of Composition on Mesostructure-Flow Interaction and Rheology of Particle Laden Interfaces

National Science Foundation

Role: PI

Dates 9/1/2014-8/31/2017

Description: The goal of this project is to characterize how changes to particle properties affect the 

microstructure and rheology of particle laden interfaces.
Contact PD/PI: Gordon, Vernita

Biosketches Page 35

BIOGRAPHICAL SKETCH

Provide the following information for the key personnel and other significant contributors in the order listed on Form Page 2. 

NAME POSITION TITLE

Jason Shear Professor

eRA COMMONS USER NAME Dept. of Chemistry & Biochemistry and

the Institute for Cellular & Molecular Biology

EDUCATION/TRAINING (Begin with baccalaureate or other initial professional education, such as nursing, and include postdoctoral training.)

DEGREE INSTITUTION AND LOCATION YEAR(s) FIELD OF STUDY (if applicable)

University of Texas at Austin B.S. 1985 – 89 Chemistry

Stanford University Ph.D. 1989 – 94 Chemistry/Neuroscience

Cornell University Post-doc 1994 – 96 Biophysics

A. Personal Statement

Prof. Shear is an expert in materials bioengineering, optics, imaging, bio-analytical measurements, and use of 

cell-culture model systems, a knowledge base ideal for the micro-3D printing studies on bacterial microencapsulation the Shear group will undertake in this collaborative project. The Shear group has been involved 

in a broad range of collaborations with microbiologists, organic chemists, physicists, and engineers, and has 

published extensively in areas related to the proposed work. Some publications relevant to the Shear group’s 

proposed contributions include:

1. “3D Printing of Microscopic Bacterial Communities,” J. L. Connell, E. T. Ritschdorff, M. Whiteley, and J. B. 

Shear, Proc. Natl. Acad. Sci. USA (2013) 110, 18380–18385.

2. “Oxygen Limitation within a Bacterial Aggregate,” A. K. Wessel, T. A. Arshad, M. Fitzpatrick, J. L. Connell, R.

T. Bonnecaze, J. B. Shear, M. Whiteley. mBio, (2014) 5, e00992-14 [1–9].

3. "Probing Prokaryotic Social Behavior with Bacterial Lobster Traps," J. Connell, A. Wessel, M. R. Parsek, E. 

Ellington, M. Whiteley, and J. B. Shear, mBio (2010) 1, e00202-10.

4. “3D Printing of Photoresponsive Biomaterials for Control of Bacterial Microenvironments,” J. L. Connell, E. T. 

Ritschdorff, J. B. Shear, Anal. Chem. published on web, Oct 2016 (DOI: 10.1021/acs.analchem.6b03440).

B. Positions and Honors

Positions: (1) Assistant Professor of Chemistry, University of Texas at Austin (9/96 – 8/02); (2) Associate 

Professor of Chemistry, University of Texas at Austin (9/02 – 9/08); (3) Professor of Chemistry, University of 

Texas at Austin (9/08 – present); (4) K. Bala Texas Instruments Visiting Professor in Bioengineering, Rice 

University (8/10 – 5/11).

Honors: National Merit Scholarship, 1985–1989; Phi Beta Kappa, 1987; Fannie and John Hertz Foundation 

Research Fellowship Grant, 1990; Howard Hughes Predoctoral Fellowship, 1990–1994; NSF Postdoctoral 

Fellowship, 1994–1996; ONR Young Investigator Award, 1997; Beckman Foundation Young Investigator 

Award, 1997; Searle Scholars Award, 1998, Alfred P. Sloan Research Fellowship, 1999; Top 100 Young 

Innovator citation, MIT Technology Review, 1999; Eli Lilly Grantee, 2000; University of Texas ICMB Fellow, 

1999–present; Beckman Scholars Advisory Panel (2003–04); Noted for a “Chemical Development of the Year” 

by C&E News (2003); Texas Academy of Sciences protegé (2004); Speaker, Paul Flory Meeting, Stanford 

University (2004); American Chemical Society Arthur F. Findeis Award in Analytical Chemistry (2005); 

Analytical Chemistry News & Features Advisory Panel (2007–present); Beckman Foundation Scientific 

Advisory Council member (2009–present); K. Bala Texas Instruments Visiting Professorship in Bioengineering, 

Rice University (8/10–5/11); Beckman Foundation Scientific Advisory Council (2009–present); Beckman Young 

Investigator Program Executive Committee (2012–present).

Page 1 
Contact PD/PI: Gordon, Vernita

PHS 398/2590 (Rev. 09/04, Reissued 4/2006)

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C. Contributions to Science

1. The Shear group developed methods for performing solution-phase chemical separations on time 

frames more than 1000-fold shorter than previously accomplished, offering insights into reaction pathways 

of transient reaction products that are more easily characterized from their electrophoretic mobilities than 

from measurable spectroscopic properties. This method, based on photochemical preparation of reaction 

intermediates, enabled compounds to be electrophoretically probed using extremely large electric fields 

over distances as small as several micrometers on timescales as small as several microseconds.Relevant 

publications include:

• “Electrophoretic Characterization of Transient Photochemical Reaction Products,” M. J. Gordon,

E. Okerberg, M. L. Gostkowski, J. B. Shear, J. Am. Chem. Soc. 2001, 123, 10780–10781.

• “Microsecond Electrophoresis,” M. L. Plenert and J. B. Shear, Proc. Nat. Acad. Sci. USA 2003, 100, 

3853–3857.

• "Microsecond Analysis of Transient Molecules using Bi-Directional Capillary Electrophoresis,"

E. Ritschdorff, M. L. Plenert, and J. B. Shear, Anal. Chem. 2009, 81, 8790 – 8796.

2. The Shear group has developed micro-3D-printing technologies for organizing cellular environments, a 

technology that allows cellular populations to be characterized under well-defined conditions and on scales 

in which ensemble behaviors begin to emerge. Of particular impact has been our use of these methods to 

probe bacterial group behaviors that underlie enhanced virulence, including quorum sensing and 

population-dependent antibiotic resistance. Relevant publications include:

• "Multiphoton fabrication of chemically responsive protein hydrogels for microactuation." B. Kaehr and J. 

B. Shear, Proc. Natl. Acad. Sci. USA 2008 105, 8850 – 8854.

• "Probing Prokaryotic Social Behavior with Bacterial Lobster Traps," J. Connell, A. Wessel, M. R. 

Parsek, E. Ellington, M. Whiteley, and J. B. Shear, mBio 2010, 1, e00202-10.

• “3D Printing of Microscopic Bacterial Communities,” J. L. Connell, E. T. Ritschdorff, M. Whiteley, and J. 

B. Shear, Proc. Natl. Acad. Sci. USA 2013, 110, 18380–18385.

• “3D-Printed Microfluidic Microdissector for High-Throughput Studies of Cellular Aging,” E. C. Spivey, B. 

Xhemalce, J. B. Shear, I. J. Finkelstein, Anal. Chem. 2014, 86, 7406 – 7412.

3. The Shear group has pioneered high-sensitivity multiphoton-based sensing technologies for 

microanalyses, developing various strategies for charactering picoliter-sized biological samples using 

capillary electrophoretic analysis. Using these methods, the Shear group demonstrated strategies for 

analyzing volumes commensurate with subcellular volumes for spectrally diverse native chromophores 

present in attomole to zeptomole quantities. Relevant publications include:

• “Characterizing Spectrally Diverse Biological Chromophores Using Capillary Electrophoresis with 

Multiphoton-Excited Fluorescence,” M. L. Gostkowski, J. B. McDoniel, J. Wei, T. E. Curey, J. B. Shear, 

J. Am. Chem. Soc. 1998, 120, 18–22.

• “Sub-Attomole Fluorescence Determination of Catecholamines in Capillary ElectrophoresisEffluent 

Streams,” M. L. Gostkowski, J. B. Shear, J. Am. Chem. Soc. 1998, 120, 12966–12967.

• “Measurements of Serotonin and Related Indoles Using Capillary Electrophoresis with MultiphotonInduced Hyperluminescence,” M. Gostkowski, J. Wei, J. B. Shear, Anal. Biochem. 1998, 260,244-250.

• “Determination of Fluorogen-Labeled Neuorotransmitters at the Zeptomole Level Using Two-Photon 

Excited Fluorescence with Capillary Electrophoresis,” J. Wei, M. L. Gostkowski, M. J. Gordon,

J. B. Shear, Anal. Chem. 1998, 70, 3470–3475.

4. The Shear group was involved in foundational work developing broad-based sensor array devices for 

analysis of various solution-phase sample types, ranging from measurements of bodily fluids such as saliva 

to determination of small-molecule components in consumables. In collaboration with a number of science 

and engineering labs at the University of Texas, Prof. Shear spearheaded a proposal during his pre-tenure 

period to the Beckman Foundation to support sensor-array development. Relevant publications include:
Contact PD/PI: Gordon, Vernita

PHS 398/2590 (Rev. 09/04, Reissued 4/2006)

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Page 37

• “Solution-Based Analysis of Multiple Analytes by a Sensor Array: Toward the Development of anElectronic 

Tongue,” J. J. Lavigne, S. Savoy, M. B. Clevenger, J. E. Richie, J. B. McDoniel, S.-J. Yoo, E. V.Anslyn,

J. T. McDevitt, J. B. Shear, D. Neikirk, J. Am. Chem. Soc. 1998, 120, 6429–6430.

• “Development of Multianalyte Sensor Arrays Composed of Chemically Derivatized Polymeric Microspheres 

Localized in Micromachined Cavities,” A. Goodey, J. J. Lavigne, S. M. Savoy, M. D. Rodriguez, T. Curey, A. 

Tsao, G. Simmons, J. Wright, S. -J. Yoo, Y. Sohn, E. V. Anslyn, J. B. Shear, D. P. Neikirk, J. T. McDevitt, J. Am. 

Chem. Soc. 2001, 123, 2559–2570.

• “Characterization of Multicomponent Monosaccharide Solutions Using an Enzyme-Based Sensor Array,” T. E. 

Curey, A. Goodey, A. Tsao, J. J. Levigne, J. T. McDevitt, E. V. Anslyn, D. P. Neikirk, J. B. Shear, Anal. 

Biochem. 2001, 293, 178–184.

• “Enzyme-Based Sensor Arrays for Rapid Characterization of Complex Disaccharide Solutions,” T. E. Curey, M.

A. Salazar, P. Oliveira, D. J. Javier, P. J. Dennis, P. Rao, J. B. Shear, Anal. Biochem 2002, 303, 42–48.

D. Research Support

Ongoing

Army Research Office 6/13 – 5/17

Role: Co-PI

“Polymicrobial virulence mechanisms in chronic wounds”

Goal: Determine mechanisms of polymicrobial interactions relevant to infections in chronic wounds

Completed in last 3 years

National Institutes of Health (1R21AI097929-01) 2/12 – 1/15 

Role: PI

"Mechanisms of antibiotic resistance in confined microcolonies"

Goal: Use of multiphoton protein fabrication to create defined, microscopic environments for 

understanding population-dependent antibiotic resistance in P. aerurinosa and other bacteria.
Contact PD/PI: Gordon, Vernita

Senior/Key Personnel: Vernita Gordon, Ph.D. PI. (effort = 2 summer months). Dr. Gordon 

will be directly responsible for image analysis of data from Aim 1 and for in vitro structuring of 

biofilms and measuring the effects of biofilm structure on microenvironement and interactions 

with neutrophils. She will also coordinate research and exchange of data, personnel, and 

training between all participants and Austin and Texas Tech as the project PI. She will direct 

experimental design, data analysis, and preparation of manuscripts

Other Personnel: Years 1-3, two full-time Ph.D. students will be involved. One student will do 

image analysis to determine in vivo biofilm structure (Aim 1) and in vitro measurements of the 

effects of biofilm structure on microenvironment, antibiotic resistance, and virulence (Aim 2).

The second student will measure the effects of mechanics and virulence on resistance to 

neutrophil phagocytosis (Aim 3). Effort will be full-time for both students.

In addition, in Year 2, one student will be supervised by Prof. Jason Shear to make 

microfabricated enclosures for bacteria (Activity 2-2). Student effort will be half time. Dr. Shear 

will contribute 0.02 summer months in scientific leadership for the half time GRA.

In Year 4, one full-time Ph.D. student will do in vitro measurements of the effects of biofilm 

structure on microenvironment, antibiotic resistance, and virulence (Aim 2).

Tuition and fees: Tuition and fees for graduate students are included, according to effort 

described above.

Travel: per year is requested for the PI and one student to attend one meeting per year 

to present data from this project, and for the students to travel to Texas Tech to meet face-toface with collaborators.

Other Direct Costs: per year is requested for Materials and Supplies in year 1, 3, and

4. We are requesting in year 2. This includes chemicals, media, glassware, and other 

supplies for culturing, and /yr for confocal microscope maintenance contract.

per year is requested for Publication Costs, which are standard for leading journals in our fields.

Budget Justification Attachment Page 50
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Funding Opportunity Number: PAR-16-242 . Received Date:

2016-11-07T15:37:27.000-05:00 Tracking Number: GRANT12284250

PHS 398 Cover Page Supplement

OMB Number: 0925-0001

Expiration Date: 10/31/2018

1. Human Subjects Section

Clinical Trial? ❍ Yes ❍ No

*Agency-Defined Phase III Clinical Trial? ❍ Yes ❍ No

2. Vertebrate Animals Section

Are vertebrate animals euthanized? ● Yes ❍ No 

If "Yes" to euthanasia

Is the method consistent with American Veterinary Medical Association (AVMA) guidelines?

● Yes ❍ No

If "No" to AVMA guidelines, describe method and proved scientific justification

3. *Program Income Section

*Is program income anticipated during the periods for which the grant support is requested?

❍ Yes ● No

If you checked "yes" above (indicating that program income is anticipated), then use the format below to reflect the amount and 

source(s). Otherwise, leave this section blank.

*Budget Period *Anticipated Amount ($) *Source(s)
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PHS 398 Cover Page Supplement

4. Human Embryonic Stem Cells Section

*Does the proposed project involve human embryonicstem cells? ❍ Yes ● No

If the proposed project involves human embryonic stem cells, list below the registration number of the specific cell line(s) from the 

following list: http://grants.nih.gov/stem_cells/registry/current.htm. Or, if a specific stem cell line cannot be referenced at this time, 

please check the box indicating that one from the registry will be used:

Specific stem cell line cannot be referenced at this time. One from the registry will be used.

Cell Line(s) (Example: 0004):

5. Inventions and Patents Section (RENEWAL)

*Inventions and Patents: ❍ Yes ● No 

If the answer is "Yes" then please answer the following:

*Previously Reported: ❍ Yes ❍ No

6. Change of Investigator / Change of Institution Section

❑ Change of Project Director / Principal Investigator 

Name of former Project Director / PrincipalInvestigator

Prefix: 

*First Name:

Middle Name:

*Last Name:

Suffix:

❑ Change of Grantee Institution

*Name of former institution:
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PHS 398 Research Plan

OMB Number: 0925-0001

Expiration Date: 10/31/2018

Introduction

1. Introduction to Application 2016_11_06_Introduction1027054233.pdf

(Resubmission and Revision)

Research Plan Section

2. Specific Aims 2016_11_06_Specific_Aims1027054147.pdf

3. Research Strategy* 2016_11_06_Research_strategy1027054151.pdf

4. Progress Report Publication List

Human Subjects Section

5. Protection of Human Subjects

6. Data Safety Monitoring Plan

7. Inclusion of Women and Minorities

8. Inclusion of Children

Other Research Plan Section

9. Vertebrate Animals 2016_11_04_Vertebrate_Animals1027054127.pdf

10. Select Agent Research

11. Multiple PD/PI Leadership Plan

12. Consortium/Contractual Arrangements combined_letters_of_commitment1027054129.pdf

13. Letters of Support Gordon_letter_from_Dan_Wozniak1027054146.pdf

14. Resource Sharing Plan(s) 2016_11_02_Resource_Sharing_Plan1026881603.pdf

Authentication of Key Biological and/or 15. 2016_11_02_Authentication_of_Resources1026881604.pdf Chemical Resources

Appendix

16. Appendix
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Introduction to Application Page 84

Introduction: This application is a re-submission of 1-R01-AI121500-01, which was reviewed in June 2015 by 

the Biomaterials and Biointerfaces Study Section. It got an impact score of 38 and was scored in the 30th

percentile. From the Summary Statement: “The strengths of the application are the unstudied area with 

innovative convincing ideas; the experience of the investigators with expertise in such measurements using 

many tools, and the study of structures that could identify new targets—‘there is much be gained.’”

We thank all reviewers for their efforts on this. In response to their critiques, this resubmission is 

substantially changed from the original submission, as follows:

Significance

Criticism: Original proposal too broad in scope. Response: We have sharpened the focus by making 

this resubmission only about P. aeruginosa in chronic wounds, rather than polymicrobial infections in multiple 

anatomical sites of chronic infection.

Criticism: Difficult to translate results between in vivo and in vitro. Response: We have added 

information on how we will measure disease outcomes (Specific Aim 1) and how we will compare those with 

our in vitro results (Specific Aim 2). We have sketched how we will respond if in vivo and in vitro results do not 

correspond (page 10). Our new Activity 3-3 gives an in vivo validation of the most novel in vitro results. 

Criticism: Some aspects of the work were already done by the team. Response: We have revised the 

scope of our proposal, so that the work proposed is entirely new, both to us and to the state-of-the-art.

Investigator

Criticism: PI Vernita Gordon is very junior and does not have enough related publications. Response: 

In 2015 and 2016, the PI published eight original research articles in leading microbiology and interdisciplinary 

journals. She led multidisciplinary teams, located in four countries on three continents, to complete work that 

has been published in mBio, npj Biofilms and Microbiomes, Langmuir, and PLoS ONE. Her leadership in 

physics and microbiology is reflected in her professional service and experience. Please see Biosketch. The 

collaborators add deep expertise in specific areas needed for this proposal.

Innovation

Criticism: No explanation of how this study will lead to new targeted drug or treatment development. 

Response: We have included new Preliminary Studies that indicate the molecular mechanisms underlying the 

different mechanical contributions of different matrix components (Aim 1). This points toward a therapy using 

competitive binding or degradation of specific matrix elements. Development of such a therapy would be 

guided by the results of Aim 3. We have changed the antibiotic-resistance work so that it now focuses on 

tobramycin (tob), PEG-y-lated tob, and bicarbonate (Aim 2). We expect to learn how to interfere with biofilm 

structure and matrix functionality such that tob and bicarbonate synergize in treatment of biofilms.

Criticism: Some of the rheological measurements and “leukocyte invasion” are standard practice. 

Response: This is incorrect. We have highlighted the novel nature of our rheology studies. We have also 

highlighted that how viscoelastic mechanics impacts susceptibility to phagocytosis is entirely unknown.

Approach Criticism: Using three different mouse models, at two different geographical sites, could 

cause site-specific factors to affect outcome. Response: We now use only one mouse model at only one site.

Criticism: Statistical treatment and identification of potential relationships were not discussed; there 

was a lack of quantifiable hypotheses. Response: We have expanded our discussion of statistical treatment 

(Research Strategy & Vertebrate Animals). We indicate the expected functional form of relationships where 

this is supported by physical understanding. Elsewhere, we describe the properties of the expected function.

Criticism: Not enough preliminary data to ensure success. Response: All our preliminary studies are 

now published in peer-reviewed journals and have been referenced in the resubmission.

Criticism: Not clear that biofilm microrheology would work. Response: We have explained our 

rheology plan in much greater detail. Microrheology is secondary to AFM work and is not required for success. 

Criticism: PNA-FISH is not needed. Response: We agree. We have changed to fluorescent bacteria. 

Criticism: Experimental plans unclear. Response: We have clarified and increased detail in all Aims. 

Criticism: Requested number of mice not well-supported. Response: Expanded Vertebrate Animals.

Environment Criticism: Three performance sites, one foreign, would make collaboration difficult.

Response: Now, only sites and colleagues in Texas are involved.

Biohazards Criticism: Any biological safety facility would be used. Response: This is incorrect. All 

animal work will be done in a certified animal facility and laboratory. All in vitro work will be done in BSL-2 

laboratories. P. aeruginosa is a BSL-2 organism, therefore this is an appropriate level of biological safety.

Foreign Organizations Criticism: Foreign participant unjustified. Response: We have removed him.
Contact PD/PI: Gordon, Vernita

Specific Aims Page 85

Specific Aims:

This proposal’s objective is to determine the impact of the spatial structure and mechanics of Pseudomonas 

aeruginosa biofilm infections, in chronic wounds, on virulence, antibiotic resistance, and immune evasion.

Most chronic bacterial infections are caused by biofilms, aggregated bacteria that are embedded in a matrix of 

polymer and protein. Unlike well-mixed, liquid cultures, biofilm infections have well-defined spatial structure. 

This spatial structure is given by the sizes of bacterial aggregates, the relative positions of aggregates, and 

matrix heterogeneity. Aggregates also have viscoelastic mechanical properties that are conferred by the 

matrix. Basic principles of material transport indicate that the spatial structure of biofilm infections must impact 

intercellular signaling, virulence, and antibiotic resistance; comparison of biofilm mechanics with known 

phagocytic forces indicate that resistance to deformation and breakup likely help biofilms resist immunological

clearance. However, there is little to no in-depth, quantitative knowledge regarding the impact of spatial 

structure and mechanics on disease course. Completion of the work we propose here will open new 

possibilities for therapeutic strategies that specifically target biofilm structure and/or mechanics.

Our long-term goal is to find new strategies for remediating biofilm infections by addressing physical properties. 

Here, our central hypothesis is that spatial structure and mechanics are the major physical factors controlling 

the development of pathogenicity, antibiotic resistance, and immune evasion in biofilm infections. This 

hypothesis is based on a synthesis of our own and others’ published work. The rationale is that completion will 

identify key physical targets for preventing, disrupting, or ameliorating biofilm infections for an important 

biofilm-forming opportunistic human pathogen. The work we propose here will also develop experimental 

techniques and understanding of an important model system that together will constitute a widely-applicable 

platform for assessing the impact of biofilm structure and mechanics for other infecting organisms.

We will test our central hypothesis and attain our objective via the following specific aims: 

1: Determine the spatial structure and mechanics of biofilm infections in wounds. For this, we will use 

sophisticated imaging to determine, in three dimensions, the size, number, locations, and heterogeneous 

matrix content of bacterial aggregates in a mouse model of chronic wound infection. We will simultaneously 

measure the density and distribution of neutrophils around the biofilm aggregates. At present, no good 

technique for measuring the mechanics of biofilm infections exists. We will develop such a technique using 

AFM microindentation and abradement of ex vivo biofilms. Working hypothesis: The structure and mechanics 

of in vivo biofilm infections in chronic wounds will follow development trajectories arising from the matrixproducing capabilities of the bacteria and pressure from the host immune defense.

2: Determine how spatial arrangements impact bacterial growth, biofilm microenvironments, antibiotic 

resistance, and virulence. For this, we will use manipulative techniques that we recently developed to recreate biofilm structures found in in vivo and in vitro environments and measure the biological changes induced 

by specific structures. Working hypothesis: Virulence and antibiotic resistance will depend on key structural 

characteristics, such as the sizes of aggregates and the distances between aggregates, through the 

development of microenvironments that differentiate as a result of the material transport and consumption of 

growth substrate, bacterial products, and antibiotics.

3. Determine the role of spatial structure and mechanics in biofilm-leucocyte interactions. For this, we 

will add freshly-isolated human neutrophils to biofilms at different stages of formation and with different 

structures and mechanics and monitor the attack by neutrophils and the bacterial response. Working 

hypothesis: Biofilm tolerance and evasion of neutrophils and their action will depend both on the neutrophils’ 

ability and speed in breaking off and engulfing pieces of biofilm, and on the ability of biofilms to kill immune 

cells.

The expected outcome of this work is a comprehensive understanding of what structures and mechanics 

develop in biofilm infection of chronic wounds, and the degree to which these structures and mechanics give 

rise to pathogenicity, antibiotic resistance, and evasion of the immune system. The results will have an 

important positive impact because they lay the groundwork to develop a new class of targeted treatments.
Contact PD/PI: Gordon, Vernita

Research Strategy Page 86

Research Strategy

A) Significance:

Chronic infections caused by biofilms annually affect 17 million Americans, cause at least 550,000 American 

deaths, and cost the US healthcare system billions of dollars [2-8]. Chronic wounds in particular can cost, per 

patient, tens of thousands of dollars per year, and are prevented from healing because they are infected by 

bacterial biofilms dominated by Pseudomonas aeruginosa [10]. Biofilm infection in chronic wounds afflicts both 

diabetic and non-diabetic patients and can lead to amputation [14].

Biofilms resist antibiotics and evade the host immune defense [10, 15-18]. In biofilms, a heterogeneous 

matrix of differentiated extracellular polymers (EPS) and proteins holds bacteria in place [19-22], thus 

controlling intercellular associations and differentiation of microenvironments [19, 23-34]. Matrix polymers and 

proteins also confer intercellular cohesion on biofilm bacteria, thereby determining the mechanical resistance 

of the biofilm to physical breakup. The impact of spatial structure and matrix mechanics on biofilm properties 

such as virulence, antibiotic resistance, and immune evasion are largely unknown. Indeed, we know little 

about what specific structures and mechanics develop in biofilm infections, and extant techniques to probe 

these properties are largely lacking. These are significant and critical unaddressed problems. 

We will bring to bear a unique combination of techniques, a number of which we have recently 

developed, for measuring and controlling the in vivo and in vitro structural and the in vitro mechanical 

properties of biofilms [9, 11, 35]. Using our distinctive combination of microbiological and physical expertise, 

we will also develop new approaches to measuring the mechanical properties of biofilms in vivo and how they 

impact resistance to immunological clearance. We will determine: what mechanical and structural properties 

develop for biofilm infections in chronic wounds in vivo; how the spatial structures and associated material 

transport in biofilm infections impact antibiotic resistance and host-damaging virulence; how virulence and 

biofilm mechanics impact resistance to immunological clearance. In short, we will contribute knowledge of 

what biofilm structures and mechanics develop in P. aeruginosa biofilm infections in chronic wounds, and the

degree to which these structures and mechanics impact the virulence, antibiotic resistance, and persistence of

the biofilm infection. This contribution will be significant because it will identify cases where structure and/or 

mechanics should be or inform specific therapeutic targets. We expect that treatments addressing physical 

properties could also be combined with traditional therapeutics for enhanced clinical outcome. In addition to 

treatments addressing virulence, antibiotic resistance, and immune evasion, our work is also likely to lead to 

improved approaches for debridement and negative pressure wound therapy.

In the short term, our work will advance understanding of an important pathogen that forms biofilm 

infections in wounds and many other anatomical sites [36-51]. Moreover, the work proposed here will develop

a platform of complementary techniques and knowledge that will be extensible to future studies of other

infection sites and other organisms, including multi-species infections and engineered microbial consortia [52- 

54]. Thus, this platform will be a foundational resource for the emerging field of physical microbiology & 

medicine. We expect that our immediate results, as well as the subsequent work building on the platform we 

develop, will lead to improved quality of life and medical outcomes, and reduced healthcare costs.

B) Innovation:

The common approaches to developing new treatments for biofilms are either to find genes important for 

forming biofilms or to directly kill the bacteria in biofilms by novel drugs. These approaches have met with only 

limited success [55]. Our goal is to determine the structural and mechanical characteristics of biofilms in vivo 

and ex vivo and to identify the impact of these physical properties on disease course. For this, we will 

implement an innovative combination of techniques from both biological and physical sciences. Our approach 

allows elucidation of the mechanistic relationship between the physical characteristics of biofilm infections and 

the course of biofilm disease that are not accessible by conventional methods.

C) Approach:

Specific Aim 1: Determine the spatial structure and mechanics of biofilm infections in chronic wounds

Introduction: The objective of this aim is to determine the spatial structures and mechanics that develop in P. 

aeruginosa biofilm infections in chronic wounds. Here “spatial structure” means the size and number density of
Contact PD/PI: Gordon, Vernita

Research Strategy Page 87

bacterial aggregates and the matrix heterogeneity within aggregates, and “mechanics” means viscoelastic 

responses to applied forces. The working hypothesis for this aim is that the structure and mechanics of in vivo 

biofilm infections in chronic wounds will follow development trajectories arising from the matrix-producing 

capabilities of the bacteria and pressure from the host immune defense. Our approach to testing this working 

hypothesis will be to use advanced imaging to assess biofilm structure and to use atomic force microscopy 

(AFM) and microrheology to measure mechanics. Both structure and mechanics will be measured in situ. The 

rationale for this aim is that P. aeruginosa is an important biofilm-forming human pathogen, but the types of 

structure and mechanics that arise in P. aeruginosa biofilm infections are largely unknown. These gaps in 

knowledge preclude identification of physical properties of biofilms as therapeutic targets.

Justification and Feasibility:

Review of Relevant Literature:

In vitro, biofilms can be millimeters or more in extent, but not in vivo [56-59]. Recent advances in 

staining and microscopy of tissue have allowed visualization of bacterial biofilms in chronic wounds, cystic 

fibrosis (CF) lungs, and other anatomical sites [1, 12, 60]. In general, in vivo biofilms are collections of 

aggregates ~10-100 μm in diameter, containing ~102

 – 106 bacteria per aggregate. In chronic wounds and 

other sites, different species are typically spatially segregated by tens of microns or more [12, 60, 61], making 

it reasonable to study single-species P. aeruginosa infections as a first step to understanding how physical 

factors impact biofilm infections.

Much work has been done to understand P. aeruginosa biofilm infections in the lungs of CF patients 

[62, 63]. Much less work has been done to understand biofilm infections in wounds, although wounds affect 

many more people: there are ~30,000 CF patients in the U.S., and ~6 million people annually are burdened 

with chronic wounds [10, 64]. Therefore, we will use CF lung infections as a test case which can guide 

investigation of wound biofilms. Biofilms in the CF lung can last for decades, under pressure from antibiotics 

and the immune system. Wound biofilm infections are not typically as long in duration as CF infections, but 

they are subject to similar pressures in vivo. Therefore, we expect that characteristics that are adaptive in CF 

infections will be beneficial to biofilms in chronic wounds as well. Chronic wound models are also expedient for 

our study because the proximity of biofilms to the surface should greatly facilitate the work in Specific Aim 1. 

The most important EPS materials for P. aeruginosa biofilms are polysaccharides (Psl, Pel, and 

alginate) and extracellular DNA (eDNA) [65-70]. In CF infections, production of alginate increases over time 

[71, 72] and worsens outcomes for patients. Alginate chemically protects biofilms by chelating reactive oxygen 

species from inflammatory cells [73, 74] and preventing activation of the complement immune system [75]. CF 

infections also evolve to increase the production of Psl, and likely Pel, with worse outcomes for patients [76- 

81]. Psl protects biofilms against antibiotics, likely by chemical binding [82], and blocks the binding of opsonins 

that promote phagocytosis [83]. We have shown that Pel also provides antibiotic protection [84]; cationic Pel 

binds to eDNA, a polyanion which binds to cationic antibiotics, such as the aminoglycoside tobramycin [85].

Thus, it is well-appreciated that biofilm matrix polymers can provide chemical protection against 

clearance. The role of mechanical protection has not been characterized, and the distinct contributions of 

matrix materials to biofilm mechanics is largely unknown. In vitro, increased alginate softens biofilms [86, 87] 

and Psl decreases but Pel increases creep compliance, the tendency to slowly deform under constant stress 

[88]. The state of the art has relied on bulk rheology, microrheology, or AFM measurements of in vitro biofilms 

[89-100]. The mechanics of biofilms grown in vivo has not been measured, even though growth conditions are 

likely to change material properties. 

Summary of preliminary data and findings:

The mechanics of biofilm infections evolve within patients. We recently determined how evolutionary 

changes in EPS production by biofilms in CF lungs are linked to changes in biofilm mechanics [11]. We use P. 

aeruginosa strains that were isolated from the sputum of four CF patients [77]. These isolates were taken at 

well-resolved timepoints over ~200-3000 days of infection, and have been characterized to determine the 

changes arising from in vivo evolution [76, 77]. We use a parallel-plate rheometer tool to apply an oscillatory
Contact PD/PI: Gordon, Vernita

Research Strategy Page 88

shear strain to biofilms (Figure 1.1) [101, 102]. We measure both elastic (solid-like) modulus G′ and viscous 

(fluid-like) modulus G′′. All moduli show only weak frequency dependence from 0.1 to 103 Hz. Plateau G′ is 

typically ~10x greater than plateau G′′, thus biofilms are dominantly solid-like (Figure 1.2). Material failure 

begins at a yield strain εY and a yield stress σY. The toughness is the energy cost to cause yielding, EnergyY. 

We group descendent isolates by whether production of alginate, Psl, or both has increased from that 

of the ancestor. We find increased Psl production alone does not change EnergyY, but increased alginate 

alone reduces EnergyY by ~2/3. However, increasing Psl along with alginate entirely rescues the loss of 

EnergyY caused by increased alginate alone. Increased alginate alone decreases plateau G′ by 90% and 

decreases σY by over 60%. However, if both alginate and Psl increase, G′ decreases by only 40% and σY is 

maintained at the ancestral value. Thus, increased Psl can counteract softening, weakening and loss of

toughness caused by increased alginate. To investigate the mechanisms by which distinct types of EPS give 

rise to distinct mechanical properties, we use isogenic strains in the PAO1 lab-strain background. We find that 

biofilms with high Psl (∆wspF ∆pel) have 3x the EnergyY, 1.8x the plateau G′, and 2.5x the σY of wild-type (WT) 

biofilms. However, the mechanical benefits of increased Psl arise only if the protein CdrA, which binds 

mannose on Pel, is co-produced [11, 103, 104]. Microscopy shows that the volume fraction of bacteria in 

biofilms is << 50%. Therefore, attachment of bacteria to the matrix should not impact the biofilm’s bulk 

mechanics. Thus, we conclude that CdrA crosslinking of Psl undergirds Psl’s mechanical benefits to biofilms. 

This is the first insight into a molecular mechanism causing the distinct mechanical impacts of EPS types. 

We find that high Pel (∆wspF ∆psl) increases EnergyY and σY by increasing the yield strain εY but not 

G′. We use atomic force microscopy (AFM) to separate pairs of bacteria. These are the first measurements of 

interbacterial cohesion. High Psl increases the energy cost to separate two bacteria by 4-6×, but high Pel 

decreases the work to separate two bacteria by 20× [11]. Thus, unlike Psl, Pel’s toughening effects are an 

emergent property of the biofilm state. Pel binds to eDNA [85], which is a significant component of the biofilm 

matrix [105-107], but is not present for the pairs of bacteria in our AFM studies. Therefore, we infer that PeleDNA binding likely toughens biofilms and increases yield strain. A possible analogy lies with double-network 

gels, in which mobile junctions and hidden length can allow large deformation without yielding [108-115].

By identifying the specific matrix components and interactions needed to generate specific mechanical 

properties, we have identified candidate approaches for disrupting specific properties via competitive binding 

and/or enzymatic degradation of matrix material. The results of Specific Aim 3 will establish which mechanical 

characteristics would be the most important to disrupt for better immunological clearance.

A 

y = 500 μm 

∆x 

B 

C 

Figure 1.1. Rheology schematic. (A) The 

rheometer tool applies a shear strain ε =

∆x/y = ε0∙sin(ωt) to the biofilm, where ω = 

angular frequency of oscillation and t = time. 

The tool’s surface is roughened to prevent 

slippage and a solvent trap prevents drying. 

To fill the tool, which has volume ~6mL, we 

pool biofilms grown on 10-15 agar plates.

(B) We measure the resulting shear stress 

response, σ = σ0∙sin(ωt + δ) = ε0∙[G' sin(ωt)

+ G'' cos(ωt)]. We fit the flat, plateau regime

and the power-law-decreasing regimes of G' 

to determine the yield point. (C) For a 

purely elastic material, the plateau value of 

G' would be the slope of the linear portion of 

the stress-strain curve. Departure from

EnergyY

ε

linearity happens at the yield point.

Integrating stress as a function of strain up 

to the yield point (area of the grey triangle) 

measures toughness, EnergyY. We include 

both elastic and viscous response in our 

measure of biofilm toughness.

Strain (%)

Figure 1.2. Elastic (G', solid symbols) and 

viscous (G'', hollow symbols) moduli for 

biofilms grown from the five related bacterial 

strains that were isolated from one CF 

patient at different points in time. Strains are 

listed in order of isolation. Isolates from later 

timepoints tend to have higher G', except the 

two mucoid isolates (A3.1 M and A4 M) 

which have high alginate production and 

lower G' than their immediate ancestors.

The biofilm with highest G' is grown by A 3.2 

D which has high Psl production. Figure 

from [11].

σ

Moduli (kPa)
Contact PD/PI: Gordon, Vernita

Research Strategy Page 89

Research Design:

Methodology: Bacterial strains: Two libraries of single-gene transposon mutants, 

in two different WT backgrounds (PAO1 and PA14), are available at nominal cost 

and allow us to elucidate the roles of specific gene products [116, 117]. We will 

focus on PAO1 because it has more possibilities for matrix variation.

Animal models for biofilm infection: We will use a mouse model for 

chronic wounds [118-120]. We have previously shown that P. aeruginosa in

mouse wounds are in a biofilm state [121-123]. Mice will be shaved and 

administered full-thickness, surgical excision wounds. The wounds will then be 

covered with a semipermeable dressing to prevent contractile healing, and 

bacteria will be injected under the dressing (a detailed description of the model,

power calculations and an animal usage table can be found in the Vertebrate Animals Section). Bacterial 

strains to be used are PAO1 WT, ∆mucA (high alginate), ∆wspF ∆pel (high Psl), ∆wspF ∆psl (high Pel) and

∆cdrA (no production of the Psl-crosslinking protein CdrA). These strains will constitutively express fluorescent 

proteins (red or green fluorescent protein (GFP) or mCherry) so that biofilms can be imaged using confocal 

laser-scanning microscopy (CLSM) (Figure 1.3). We will use DAPI to visualize inflammatory cells. We will 

sacrifice animals at 24 & 72 hours and 7 days after infection and harvest tissue from the infection site. 

Harvested samples will be fixed and sectioned. 

As assays for disease outcomes, for all animals we will determine: systemic spread of bacteria, as a 

proxy for virulence; quorum sensing, ex vivo using fluorescent reporter strains; antibiotic efficacy, ex vivo using 

measurements of colony-forming units; and inflammation, wound closure and healing, as follows:

To measure systemic bacterial load, spleens will be excised, weighed, dispersed in sterile PBS, serially 

diluted, and plated on Pseudomonas isolation agar to quantitate CFU/g tissue. To measure antibiotic efficacy, 

we will use a similar procedure on tissue sections from infected wounds, which will first be suspended in 90

μmol/L tobramycin or PBS for 5 hours, and then treated as above. We will image wounds daily using the 

SilhouetteStar laser-scanning wound imaging, 3D measurement and documentation system (ARANZ Medical) 

and percent wound closure will be calculated. Wound tissue histology via hematoxylin & eosin and Masson’s 

trichrome staining will be used to assess wound healing as previously described [123-125]. The inflammatory 

response will be assessed using a Qiagen Cytokine Multi-Analyte ELISArray Kit and histological assessment of 

neutrophil infiltration. Also, since weight loss indicates a progressing infection, all mice will be weighed daily.

Activity 1-1: Determine the structures of P. aeruginosa biofilm infections as a function of 

infection time and matrix production capability. We will use confocal laser-scanning microscopy (CLSM) to 

measure the spatial structures of P. aeruginosa biofilm infections as they form in vivo. We will use quantitative 

image analysis, in Matlab, to turn micrographs into quantitative measurements. The PI has expertise in 

quantitative microscopy and image analysis [9, 35, 84, 126-144]. Thus we are well-positioned to develop new 

measurement metrics as needed during the progress of our work. Initially, we will determine the size 

distribution of bacterial aggregates and the three-dimensional positions and number density of bacterial 

aggregates with respect to each other. We will also measure the number and spatial distribution of 

neutrophils, as in [1, 145], and correlate neutrophil density with the size and position of aggregates. We expect 

the aggregate size distributions to show a peak value that increases with early infection time and biofilm 

growth, and then plateaus as the aggregates hit size limits that arise from limiting oxygen, which we expect to 

depend on the density of surrounding neutrophils [1]. Because this limits aggregate growth beyond a certain 

size, we also expect the width of the size distribution to decrease with time. We expect that if matrix 

production capabilities impact the size distribution, then matrix content with diminished mechanics (Activity 1-3) 

linked with better clearance by neutrophils (Specific Aim 3) should be associated with smaller aggregate sizes. 

We expect the sizes of individual aggregates to impact the development of microenvironments via

diffusion within aggregates (Aim 2). For an isotropic 3D environment, the density of diffusing material φφ is a

function of position rr⃗ and time tt, thus: ∂∂φφ(rr⃗,tt) = DD∇2φφ(rr⃗, tt); ∇ is the gradient operator and DD is the diffusion

∂∂tt

200 μm

Figure 1.3. Aggregates of P.

aeruginosa (green) and S. 

aureus (red), in a mouse 

wound. We visualized these 

using CLSM (unpublished).
Contact PD/PI: Gordon, Vernita

Research Strategy Page 90

coefficient, which has dimensions of length2/time. Therefore, for a structural metric characterizing diffusive 

transport between aggregates, we will use spatial moment analysis to find the mean and variance of the 

square of the inter-aggregate distance, which we expect to remain roughly constant with time. If not, we will 

use knockout mutants to probe the roles of motility, dispersal, and chemotaxis in developing biofilm structure.

In addition to possible interchanges and exchanges of motile bacteria with each other and their 

environment, we expect that aggregates may be able to interact through the exchange of diffusible signals and 

sequestration of diffusible antibiotic. To date, no good technique for measuring the transport properties of in 

vivo infection sites exists. We will work to develop a new technique to do so by co-inoculating fluorescent 

beads and quantum dots of different sizes and surface functionalities into animal models, along with bacteria, 

and measuring how the spatial distribution of these tracer particles changes with time. This will give us 

measures of the effective diffusion constants, plus additional transport through flow or animal movement, for 

materials of different sizes and surface functionalities within the wound bed. If our analysis of these results 

indicates that transport properties of the environment change significantly with time, we will add differentlylabeled tracers to the wound at different timepoints after inoculation, and measure how their positions vary as a 

function of time. Since transport is fundamental to any intercellular process, especially so in biofilm infections 

containing multiple spatially-segregated, but interacting, pathogens, plus host cells, we expect that our 

technique will be foundational for future studies of biofilm infections and of the healthy microbiome.

Determining the internal structure of biofilms in terms of heterogeneous matrix content is a challenge, 

since most stains for biofilm matrix materials also stain host tissue. To overcome this difficulty we will use 

quantitative image analysis to distinguish differential binding – we expect that stains for biofilm matrix materials 

will have higher affinity for the biofilm (which we will measure as greater brightness) than the host tissue. We 

will validate this expectation by comparing biofilms that over-express specific EPS materials with WT biofilms. 

There, we expect over-expressing biofilms to be brighter in the relevant stain, with respect to the surrounding 

tissue, than the WT. We used a similar approach recently to distinguish specific and non-specific binding of a 

Psl stain [129]. To determine the spatial distribution of Pel, Psl, alginate, and eDNA, we will stain harvested 

biofilms using antibody and lectin for Psl, lectin for Pel, propidium iodide for eDNA, and cationic dyes for the 

polyanion alginate, as in [146]. We will get Psl stains from Prof. Dan Wozniak and Pel stain from Prof. Matt 

Parsek (see letters). The other stains are commercially available.

In comparing the matrix content and heterogeneity of biofilms grown in vivo with those of biofilms grown 

in vitro (Specific Aim 2), we will determine whether eDNA content is higher, overall or near the periphery, for 

biofilms grown in vivo. If so, this would be consistent with our and others’ finding that P. aeruginosa biofilms 

can incorporate eDNA from neutrophils [121, 147]. Neutrophils can be lysed by bacterial virulence factors and 

can also release eDNA-rich extracellular traps as part of the innate immune response [148-152].

Activity 1-2. Determine biofilm mechanics as a function of matrix content and infection time. The 

primary means of mechanical characterization of the in-vivo wound biofilms will be through ex-vivo 

measurements done using an AFM. We will use ex vivo samples, specifically biopsies containing biofilms that 

will be harvested from mouse wound beds at the timepoints and for the bacterial strains described above under 

Methodology. These samples will be placed onto an agar plate and kept submerged within a growth broth. 

These samples will then be characterized using an Asylum Research MFP-3D SA AFM in a liquid environment. 

We can characterize samples over their entire 2D area; samples with lateral dimensions ~100 μm up to orders 

of magnitude larger can be probed. Keeping samples in a liquid environment will ensure that the tested 

material is as close to in-vivo state as possible. All tests will occur as quickly as possible after the biofilms are 

excised, always less than 12 hours.

First, we will use the AFM in tapping mode to determine both the topography of the biopsy sample and 

the location of the biofilm. In tapping mode, the AFM will provide a topographical height map and a qualitative 

stiffness map of the sample, which we will use to distinguish regions of biofilm from regions of tissue [153-155]. 

Then, we will do a Force-Volume mapping. The AFM tip will be rastered over the 2D sample area, and will 

measure force-displacement curves using a cantilever with a round, large silica probe. From these curves, 

biofilm elasticity can be obtained using an appropriate contact model. Typically a Hertz or Sneddon model is
Contact PD/PI: Gordon, Vernita

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used [100, 153, 154], assuming no adhesion between probe and sample; however, many other possible 

models include adhesion and can be used for biological samples [156]. Thus, we will measure the relative 

stiffness of the biofilm with respect to tissue. We will then run the AFM in a constant force mode while 

measuring the displacement. This will yield the relaxation time spectrum of the biofilm directly, from which we 

will estimate viscosity by assuming the biofilm acts as a Maxwell element (i.e., a spring and dashpot in series).

The above measurements will provide relative stiffness, elasticity, and relaxation times, but will not truly 

probe system viscoelasticity. To get truer values of biofilm G' and G'', we will use a more advanced technique, 

Amplitude and Frequency Modulation [153]. By forcing the cantilever to vibrate at a controlled frequency and 

amplitude before contact with the biofilm, the amplitude change and frequency change due to the biofilm can 

be related to viscoelastic moduli; this is similar to results obtained in a rheometer as described in Preliminary 

Data, but with in situ measurement and high spatial resolution. This mode runs automatically on our AFM. 

Rastering over the sample will provide a map of these moduli similar to the Force-volume stiffness map.

AFM work requires removing the samples from the animal. Mechanical characterization in vivo is more 

difficult, but it would allow us to verify that the ex vivo biofilm mechanics correspond to the in vivo biofilm 

mechanics. Therefore, we will attempt microrheology in vivo. In two-particle passive microrheology, the crosscorrelated thermal motion of pairs of particles can be related to viscoelastic moduli, over a range of frequencies

ωω [157, 158]. The displacement uu(ωω) of a single particle is given by the Stokes-Einstein relationship uu(ωω) = 

ff(ωω) 

6ππππππ(ωω)

, where ff(ωω)is a Brownian force and ππ(ωω) = ππ′ + iiππ′′ is the complex shear modulus. Here, if colloidal

probes from Activity 1-1 incorporate into biofilms, we will take high-speed, 3D movies of colloids moving in the

biofilms in vivo. A high-speed confocal fluorescence microscope is available in the Materials Characterization 

Facility at TTU. If tracer particles from Activity 1-1 incorporate into biofilms, we will also use magnetic beads for 

active microrheology. Inexpensive, high-precision magnetic tweezers can apply stresses up to ~25 kPa, 

comparable to the yield stresses we measure for biofilms grown in vitro [159]. Thus, we expect to measure 

local yielding as well as viscoelasticity. Microrheology in vivo has a number of potential difficulties, and so will 

be a secondary analysis technique intended to supplement the primary AFM analysis [160, 161].

Expected Outcomes: The overall outcome of this aim will be comprehensive knowledge of the 

structural and mechanical characteristics of P. aeruginosa biofilm infections that develop in chronic wounds. 

This knowledge will be used to guide our work in Specific Aims 2 and 3.

Potential Pitfalls and Alternative Strategies: We expect the results from in vivo models to reveal 

common themes of structure and mechanics controlled by infection time and matrix production capability. If we 

measure changes in structure or mechanics that do not result from changes in EPS or protein content, we will 

investigate whether this could arise from varying pH or salt concentration between sites. We will also 

investigate other possible causes such as cross-linking by pili or flagellae, or degradation by host enzymes or 

reactive oxygen species from host neutrophils [103, 162].

Specific Aim 2: Determine how spatial arrangements differentiate into distinct microenvironments

Introduction: The objective of this aim is to determine how distinct spatial structures result in the 

development of microenvironments that impact biofilm disease. The working hypothesis for this aim is that 

virulence and antibiotic resistance will depend on key structural characteristics, such as the sizes of 

aggregates and the distances between aggregates, through the development of microenvironments that 

differentiate as a result of the material transport and consumption of growth substrate, bacterial products, and 

antibiotics (Figure 2.1). Our approach will be to recreate the salient structural features of biofilm infections in 

vitro and then measure the oxygen gradients, antibiotic resistance, virulence, and quorum sensing in the 

resulting microenvironments. The rationale for this aim is that knowing the effect of structure on clinical 

outcomes will indicate when it is appropriate to target a particular structure for treatment, and could help open 

the way for treatments based on interfering with the physico-chemical microenvironments of biofilms.

Justification and feasibility:

Review of the relevant literature:
Contact PD/PI: Gordon, Vernita

Research Strategy Page 92

In vitro, the size and proximity of bacterial aggregates

impacts virulence and antibiotic resistance. Small, dense

populations of ~150-1000 cells in a pL volume can activate quorum 

sensing and develop phenotypic antibiotic resistance [163-169]. 

Quorum sensing controls gene expression according to the density 

of like neighbors [170-174]. Bacteria produce autoinducers and

sense their concentration. When autoinducer concentration is

high, quorum sensing activates [175] and, for P. aeruginosa, 

increases the production of virulence factors [176-178]. Even

aggregates that are separated by tens of microns or more can

interact through chemical signals [179, 180]. Oxygen depletion,

which arises in aggregate interiors as bacteria near the surface

consume oxygen, can also impact quorum sensing and virulence 

[181-187]. Oxygen depletion also slows growth, which can lead to

antibiotic resistance because the mechanism of activity of many antibiotics makes them more effective against 

rapidly-growing bacteria: e.g., aminoglycosides bind to the ribosome and disrupt protein synthesis.

The composition and structure of biofilm matrices impacts antibiotic resistance. Psl protects biofilms 

against antibiotics, likely by chemical binding to antibiotics [82]. We have shown that Pel also provides 

antibiotic protection [84]. This likely arises because cationic Pel binds polyanionic eDNA along the biofilm 

periphery, where it is thought to electrostatically bind to cationic antibiotics, such as the aminoglycoside 

tobramycin [85]. Binding antibiotics at the biofilm periphery would hinder high concentrations of antibiotic from 

penetrating the biofilm and thus reduce the effective concentration of antibiotic to which bacteria are exposed, 

as long as the surrounding EPS is not saturated with antibiotic.

Preventing antibiotics from binding to the biofilm matrix can increase antibiotic efficacy. Tobramycin 

(tob) is an aminoglycoside antibiotic that is the front-line drug for many P. aeruginosa infections [188]. Prof. 

Hugh Smyth (Pharmacy, UT Austin), has recently found that tob that has been chemically conjugated with 

polyethylene glycol (tob-PEG) is 3x more effective against mature P. aeruginosa biofilms (treated after 24 

hours of growth, the concentration corresponding to 80% inhibition of activity (MIC80) is 27.8 μmol/L) than is 

conventional tob (MIC80 = 89.8 μmol/L) [189]. This likely results because PEG functionalization reduces the 

binding of tob to biofilm matrix polymers and not from an intrinsic increase in drug activity: tob-PEG is 10x less 

effective against planktonic P. aeruginosa (MIC80 = 14 μmol/L) than conventional tob (MIC80 = 1.4 μmol/L).

Summary of preliminary data & findings:

Biofilm-specific antagonisms between antimicrobials. We and others have shown that high pH 

synergizes with aminoglycosides in killing exponentially-growing planktonic bacteria [13, 190-192]. Thus, 

combining an aminoglycoside with an adjuvant base has promise for re-empowering an established class of 

antibiotic. This could combat rising antibiotic resistance and the dwindling supply of new antibiotics and reduce 

toxic side effects by lowering required dosage [193-195]. However, we find high pH antagonizes with tob in 

biofilm treatment (Figure 2.2) [13]. Tob+base acts additively against stationary-phase planktonic bacteria, so 

antagonism per se does not result from low growth. Biofilms with high Psl show the greatest antagonism 

(Figure 2.2D), so we anticipate that antagonism most likely arises because tob binds to the biofilm matrix.

Controlling biofilm structure. We have developed a novel way to structure flow-cell biofilms using an 

optical trap to build arbitrary configurations of bacteria with single-cell resolution, including co-patterning of 

distinct strains [9]. Under the microscope, we can measure how subsequent biofilm development depends on 

structure (Figure 2.3) [9]. The microscope stage is enclosed in a light-tight incubator to allow biofilm growth at 

physiological temperature with continual monitoring. This approach imposes no barriers to inter-aggregate 

transport or accessibility of aggregates to immune cells, and it results in structures comparable in size to those 

measured in vivo (compare Figure 2.3 and Figure 3.1). Other methods of structuring biofilms either enclose 

bacteria or structure biofilms on lengthscales much greater than in vivo [30, 196-201].

Figure 2.1. Structural characteristics of 

biofilm infection, such as aggregate size, 

inter-aggregate spacing, and heterogeneous 

distribution of matrix materials, should give 

rise to differentiated microenvironments that 

enhance antibiotic resistance and virulence.
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Research Strategy Page 93

Research Design:

Methodology: We will use optical

trapping to create biofilms with spatial 

structure that mimics what we find in

Activity 1.1 in terms of aggregate size, 

inter-aggregate proximity, and intraaggregate heterogeneity. We will use

bacterial strains with different profiles

of matrix production; strains are

optically-distinguishable via production 

of different fluorescent proteins. To

confirm and measure local polymer

content, we will use staining as in 

Activity 1-1. 

Optical trapping is uniquely

advantageous as a way to structure

biofilms because it allows construction 

of biofilms with user-controlled

structure. However, in wound

infections and many other scenarios,

bacterial aggregates are suspended,

not attached to a surface [15, 202,

203]. Furthermore, we expect material

transport in wound infections to be

diffusive (c.f. Activity 1-2), not

convective as for inter- and extraaggregate transport in a flow cell.

Therefore, to better re-create

environmental properties of in vivo

biofilms, we will also use biofilms grown as suspended

aggregates in three-dimensional soft gels of agarose or agar.

Others have found that P. aeruginosa and Staphylococcus

aureus aggregates (~ ≤100 μm in radius) display biofilm traits

such as antibiotic resistance, differentiation, and growth

limitation due to nutrient and oxygen depletion [204, 205].

To best represent wound conditions, we will also use an in vitro model based on chopped-meat media, 

with heparinized bovine plasma and horse red blood cells [206]. This contains physiological concentrations of 

blood components. We and others have used this model to grow polymicrobial biofilms that accurately reflect 

the microbial populations and morphologies of human and mouse wound infections [124, 206-208].

By varying the number density of bacteria initially incorporated into the gel, we will vary the interaggregate spacing; the size of aggregates varies with distance from the interface where nutrient and oxygen 

are supplied [204]. Thus, we will reproduce the aggregate sizes and inter-aggregate spacings that we 

measure in vivo. Gels also allow high-throughput measurements in a way that optical trapping does not.

Others have shown that the EPS Psl can act as a signal to increase levels of the second messenger 

cyclic-di-GMP, which changes the expression patterns for many genes [209]. Therefore, to confirm that the 

effects of EPS result from transport and not from signaling, we need to restrict full physical and chemical 

access to bacterial microcolonies for a subset of experiments. For this, we will use micro-3D (μ3D) printing 

that we developed to encapsulate bacteria and grow microcolonies within picoliter containers of defined size 

and arbitrary shape [196, 197, 210]. Walls are formed from cross-linked proteins and provide a physical

Figure 2.3: Biofilm

structures created by

optical trapping. We placed

10 P. aeruginosa in an 

isotropic field of S. aureus. 

Six hours later, the initial

P. aeruginosa structure has propagated into S. aureus the developing biofilm [9].

T/T50 Classic, 

planktonic T/T50 Classic, 

biofilm

B/B50

pH

T/T50 High Psl, 

planktonic

Tobramycin

(μg/mL)

B/B50

pH

High Psl, biofilm

B/B50

pH

Bicarb.

(mM)

pH

Figure 2.2 We use response surfaces to measure the effect of tob and 

bicarbonate (bicarb) combinations on (A,C) planktonic bacteria and (B,D) 

biofilms of (A,B) a CF clinical isolate with “classic” phenotype and (C,D) a 

CF isolate with high Psl. (A-C) Tob and bicarb concentrations are plotted as 

the fraction of the concentration corresponding to 50% inhibition of growth 

(MIC50). (D) MIC50 is not well-defined for this system, so actual

concentrations are used. (A,C) The planktonic response surfaces are 

concave-upward, reflecting synergy between tob and bicarb. (B,D) The 

biofilm response surfaces are concave-downward, reflecting antagonism 

between tob and bicarb. (C,D) The high-Psl isolate shows greater

antagonism in the biofilm state than does the classic isolate, even though 

the high-Psl isolate shows greater synergy in the planktonic state. (D) 

Portions of the biofilm response surface extend above 0% change, indicating 

that treatment has enhanced biofilm activity. All panels from [13]. % change % change % change % change
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Figure 2.4: Bacterial

microenclosure.

boundary for segregating cells while supporting diffusion of different molecular types and sizes depending on 

the matrix composition and crosslinking density (Figure 2.4).

We will begin by recreating published in vivo biofilm structures [61, 

211], and then build on the results from Activity 1-1. We will use wide-field 

epifluoresence microscopy and confocal laser-scanning microscopy (CLSM) 

for measurements. We will measure antibiotic resistance using live-dead 

staining, and quorum sensing and virulence using reporter strains of bacteria

that express green fluorescent protein (GFP) in proportion to the activity of the rsaL and rhl genes. We will 

record growth physiology using a plasmid for GFP [212] that will only be expressed in metabolically-active 

cells, and using quantitative FISH [213]. We will measure oxygen concentration and pH using fiber optic and 

electrochemical microsensors [12, 214-217].

We will verify the in vivo relevance of the in vitro microbiology studied below by comparing the results 

found below with the disease outcomes found with different biofilm structures in Specific Aim 1.

Activity 2-1: Determine the effect of biofilm spatial structure on growth physiology and 

microenvironment. We will determine the degree to which the distinct structures found in biofilm infections 

alter bacterial growth and microenvironment, both of which are linked to antibiotic resistance. We expect to 

find that bacteria in small aggregates, near biofilm exteriors, and near the inlet or interface where growth 

substrate is supplied, will grow more quickly than bacteria in biofilm interiors due to oxygen and nutrient 

limitation. Our published work and the work of others indicates that, for a given exterior concentration of 

growth substrate, the periphery of aggregates will contain a layer of actively-growing bacteria that is constant in 

thickness regardless of aggregate size, and an interior of quiescent or very slow-growing bacteria that fills the 

rest of the aggregate volume [35, 218, 219].

Activity 2-2 Determine the degree to which structure impacts the antibiotic tolerance of biofilm 

infections. We expect this to depend on biofilm structure both directly, via the matrix content and 

heterogeneity, and indirectly, via growth physiology and microenvironment. We believe that PEG-tob should 

be able to overcome tob’s tendency to bind to the matrix and thereby make tob+bicarbonate combinations 

synergistic against biofilms. Moreover, we expect that the spatial structure of heterogeneous matrix content 

will maximize resistance to tobramycin, and antagonism between tob+bicarbonate, when tob-binding matrix 

polymers such as Psl and eDNA are located near the biofilm periphery, because this will minimize transport of 

tob into the biofilm interior.

In addition to optical trapping to control matrix heterogeneity, we will also use μ3D-printed core-shell 

communities to confirm that EPS confers antibiotic protection by binding to antibiotic and thereby hindering 

transport, and not via any mechanism requiring direct contact with cells. EPS non-producers will be 

encapsulated in cores surrounded by shells, of varying thickness, containing EPS producers or EPS extracts 

(Figure 2.4). We will tune the wall thickness, composition, and cross-linking density to make barriers 

permeable to antibiotics but impermeable to high molecular-weight EPS. We also have the option to eliminate 

the outer shell, so that producers in bulk solution cover a space extending essentially to infinity.

Measurement endpoints will be killing of bacteria if this happens, and the achievement of steady-state 

antibiotic distributions if not. We will measure the distribution of antibiotic using fluorescently-tagged drugs and 

using hydrophilic fluorophores without drug conjugation.

Activity 2-3: Determine how structure impacts the upregulation of virulence. We expect virulence in the 

quorum-sensing regulon to depend on the number density and size of aggregates. We will use GFP reporter 

strains to measure the upregulation of P. aeruginosa virulence factors and of quorum sensing. As controls, we 

will use P. aeruginosa mutants that are incapable of responding to quorum sensing signals. We expect that the 

structure of P. aeruginosa biofilms that maximize virulence upregulation caused by quorum sensing will be set 

by a competition between high cell number and density (which will tend to increase the local concentration of 

autoinducers) and low metabolism in oxygen- and nutrient-limited large bacterial aggregates.
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Expected Outcomes: The outcomes of this aim will be an understanding of how key characteristics of 

biofilm structure impact the development of microenvironments that lead to two important properties of biofilms

– antibiotic tolerance and virulence. This will open up the possibility of manipulating biofilm structure and 

microenvironments to make them more amenable to antibiotic treatment, or to treatment with less-toxic 

combinations of antibiotics, and/or to make biofilms less virulent.

Potential Pitfalls and Alternative Strategies: Our working hypothesis is that virulence and antibiotic 

resistance will depend on key structural characteristics. This hypothesis is based on basic principles of mass 

transport and is unlikely to prove invalid in vitro. However, it is possible that our in vitro measurements may 

not correspond with in vivo outcomes. This could result from differences in the transport in in vitro and in vivo 

environments, or pH that alters chemical stability. Published measurements of biofilm structure ex vivo are 

compatible with aggregates that are patterned laterally, in a 2-D plane, as we did in [9]. If we find in Activity 1- 

1 that we need to structure biofilms in the z-direction as well, we will use μ3D-printed microenclosures [163, 

180, 210] or solidify gel on top of bacteria placed by optical trapping [28, 220, 221], and then arrange more 

bacteria on top. We can also use low-cost bioprinting available from SE3D, who will consult with us on 

developing their current technology to be able to structure biofilms (see letter from CEO Dr. Mayasari Lim).

Specific Aim 3: Determine the role of mechanics and virulence in biofilm-neutrophil interactions

Introduction: The objective is to determine how mechanics and virulence interplay to impact biofilm evasion 

of the host defense. The working hypothesis the bacterial tolerance and evasion of neutrophils will depend 

both on the neutrophils’ ability and speed in breaking off and engulfing pieces of biofilm, and on the ability of 

biofilms to kill immune cells. Our approach to testing this working hypothesis will be to add freshly-isolated 

human neutrophils to gels with tunable mechanics that recreate biofilm mechanics and to structured biofilms 

and measure the neutrophils attack on the bacteria and the bacterial counterattack. The rationale is that 

chronic biofilm infections are not removed by neutrophils, but little is known about why. In CF most lung 

damage comes from reactive oxygen species (ROS) released as a result of frustrated phagocytosis [222, 223]. 

Reducing ROS release by enhancing phagocytosis would slow the cumulative destruction of lung tissue. We 

have found that in wounds biofilms are surrounded by high numbers of neutrophils, but many of them are dead 

and, counter-intuitively, enhanced neutrophils response enhances biofilm formation (perhaps because eDNA 

from neutrophils is incorporated into biofilms) [121]. Enhancing phagocytosis should cause neutrophils to 

repress, rather than enhance, biofilm development. Moreover, mechanics-targeting strategies that enhance 

the susceptibility of biofilms to phagocytic clearance would not be hindered by the rise in antibiotic resistance.

Justification and feasibility:

Review of the relevant literature:

Neutrophils are first responders to infection

[224] that easily engulf planktonic bacteria 

[217, 225]. However, mature biofilms are 

protected against phagocytosis despite

being surrounded by continually-recruited neutrophils that do not penetrate the biofilm [1, 12, 15, 16, 18, 145, 

217, 226-232] (Figure 3.1). The mechanism(s) by which biofilms are protected are not fully known [18, 217, 

233-236], although physical hindrance, slow bacterial growth, and virulence have been implicated. In 

particular, the role of biofilm mechanics in evasion of the immune system is not known.

Because ~10 μm neutrophils are an order of magnitude smaller than the ~100 μm biofilm aggregates 

(Figure 3.1), for neutrophils to phagocytose biofilm bacteria they must be able to break off a piece of the 

biofilm which is small enough for them to ingest [237]. It has been estimated that neutrophils apply a stress of

~1 kPa during phagocytosis [238]. This stress is within the range of G' values we measure for biofilms (Figure 

1.2) and suggests that the mechanics of a biofilm is likely to impact its resistance to phagocytosis.

Phagocytosing blood granulocytes and macrophages also exert stresses of ~1 kPa [239, 240]; phagocytosing 

Dictyostelium and Entamoeba can break off and ingest small pieces of a target [241, 242].

Biofilm mechanics are also likely to impact the timescale of phagocytosis. Changes in timescale matter

A B Figure 3.1. P. aeruginosa biofilm

aggregates surrounded by

neutrophils (A) in a CF lung [1] and

(B) in a chronic wound [12]. 

Bacterial aggregates (red, green and 

white arrows) are surrounded by

neutrophils (blue, red arrow).
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KKmm+ [LL]mm dd

because bacteria-produced virulence factors can kill neutrophils and other immune cells [243-245]. Delays 

that give more time for virulence factors to act should help protect the biofilm. Mature, large biofilms produce 

rhamnolipid that lyses neutrophils [244]. Quorum sensing upregulates production of pyocyanin, which induces 

neutrophil apoptosis and impairs neutrophil-mediated host defense [245]. Therefore, we expect that the ability 

of biofilms to kill neutrophils using virulence factors will also depend on the biofilm structure (see Activity 2-3).

Research Design:

Activity 3-1. Determine the role of mechanics in the biofilm’s evasion of neutrophil phagocytosis. We 

will use gels to recreate dominant aspects of the biofilm mechanics we measure in our preliminary studies for 

Specific Aim 1 and in Activity 1-2 – namely the elastic modulus G', the yield stress σY, and the yield strain εY. 

Agarose and polyacrylamide gels are well-established for studying the effects of substrate mechanics on 

eukaryotic cells. For agarose gels, G' can be tuned using both concentration and molecular weight, from 

below 1 kPa to over 1 MPa [246]. For polyacrylamide, both empirical and analytical relationships for G' as a 

function of acrylamide and bis-acrylamide content exist [247, 248]; G' can be tuned from 0.5 to 50 kPa. Thus, 

the range of gel moduli available compares well to the range of biofilm moduli we measure (Figure 1-2).

We will add freshly-isolated human neutrophils to gels, in liquid serum media. The isolation protocol 

comes from Prof. David Greenberg, U. T. Southwestern Medical Center (see letter), and is similar to published 

protocols [1, 18, 249]. We will incorporate live bacteria into gels to make them immunogenic. We will use two 

assays: (1) Incubate neutrophils in multi-well plates coated with gel containing fluorescent beads. After 

rinsing, we will measure neutrophil fluorescence using a plate reader or flow cytometer; the greater the 

increase in fluorescence, the more successful the neutrophils at phagocytosis. We will also use fluorescence 

to measure the change in gel volume in wells. This high-throughput approach is inspired by previous work on 

phagocytosis of biofilms [83] and will allow us to rapidly survey the impact of a wide range of elasticity and 

yielding values. (2) Record the interactions of neutrophils with gels (formed on glass coverslips coated with 

fibrinogen or poly-L-lysine as in [83]), at 37°C, using a microscope. Bacteria and embedded beads will be 

tracers for traction force microscopy measurements of the time-dependent stresses, strains, yielding, and 

engulfment resulting from neutrophils’ phagocytic attempts [250, 251].

We expect to find ranges of G' and σY such that, for long incubation times, susceptibility to 

phagocytosis decreases with increasing G' and σY. Outside these ranges, we expect phagocytosis to be 

constantly high for low G' and σY, and constantly zero or very low for high G' and σY. Thus we will bracket a 

“window” of G' and σY for which disrupting biofilm mechanics could increase susceptibility to phagocytosis. We 

also expect to find a range of εY such that, for constant σY, the timescale required to complete phagocytosis will 

increase with εY. This will reveal a “window” of εY where disrupting biofilm mechanics could increase the speed 

of phagocytic clearance. Should we find that the timescale for clearance is not well-described as an increasing 

function of εY/σY, we will investigate the role played by viscous contributions to EnergyY. We will also 

determine if the stresses exerted by phagocytosing neutrophils vary with G' - substrate G' impacts neutrophil 

morphology and migration [252], stresses exerted by migrating fibroblasts and Dictyostelium [253-255], the 

macrophage foreign body response and adhesivity [256, 257], and phagocytosis of small solid particles [258].

Activity 3-2. Determine how upregulation of virulence impacts immune evasion. In vitro, we will 

create configurations of aggregates found in vivo (Activity 1.1) that have different levels of virulence (Activity 2- 

3). We will use microscopy and reporter strains for virulence genes to determine the biofilms’ response to and 

killing of neutrophils. We will also confirm the link between structure, virulence, and resistance to neutrophils 

using bacterial strains that constitutively over-express rhamnolipids and/or pyocyanin and strains for which 

virulence is inducible by addition of arabinose to the growth medium. We expect that killing by virulence 

factors will likely be described by a Hill function, which describes a variable ligand concentration [L] (here the 

concentration of a particular virulence factor) binding randomly to receptors with disassociation constant Kd: 

HH([LL]) = [LL]

mm

; m measures the self-cooperativity of the ligand and the slope of the linear regime of the

sigmoidal curve HH([LL]). This form of dose-response function has been seen for many antimicrobials, by us
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and others [13, 259-261]. We will analyze the interaction of multiple types of virulence factors using doseresponse surfaces, as we and others have done for interacting antibiotics (Figure 2.2) [13, 262-264]. Here we 

expect to find additive or synergistic interactions. We will also use dose-response surfaces to analyze the 

interaction of mechanics with virulence. For this, one “concentration” axis will measure the timescale required 

for phagocytic engulfment (Activity 3-1). We expect synergy between virulence and engulfment timescale.

Activity 3-3. Validate immune evasion results from the previous activities in vivo. To confirm the the in 

vivo impact of mechanics and virulence on neutrophil phagocytosis of biofilms, we will make “model” biofilms 

by creating gel beads with the most starkly distinct absolute susceptibility to phagocytosis and timescale for 

phagocytosis, as determined in Activity 3-1. We will embed bacteria into gel beads, using both WT and a 

highly-virulent strain so that we can probe the interplay between phagocytosis timescale and virulence. 

Bacteria-impregnated gels will be inoculated into mouse wounds and inflammation, wound closure and healing, 

and bacterial load will be measured at 4 and 7 days post-innoculation. We expect to find that low mechanical 

susceptibility to phagocytosis and high virulence synergize to worsen disease outcomes.

Expected Outcome: The expected outcome is knowledge of what windows of elasticity and yielding, 

virulence levels, and changes therein have potential for promoting better immunological clearance. This will 

open up the possibility of manipulating biofilm mechanics and/or structure and microenvironments (which we 

expect to impact the production of virulence factors) to counteract biofilms’ evasion of the immune system.

Potential Pitfalls and Alternative Strategies: The working hypothesis for this aim is that a biofilm’s 

evasion of the immune system depends on both the mechanics of the biofilm and its production of virulence 

factors. This hypothesis is based on the literature and our own results but it carries a measure of risk, since 

very little is known about how biofilms evade the host immune system, and because these types of 

measurements are new and new protocols will have to be developed. If the agarose and polyacrylamide gels 

resist phagocytosis despite provoking an immune response, we will first test whether they are too stiff, and/or 

have yield stress too high, for neutrophils to overcome. To extend the range of mechanics assayed to softer, 

weaker materials, we will use alginate and other hydrogels with moduli that are tunable even lower [265-269]. 

Should we find that, even in this case, mechanics do not contribute to immune evasion, we would use AFM 

and shear flow to measure the strength of adhesive forces between neutrophils and biofilms with different 

polysaccharide production patterns. We anticipate that stronger adhesion between neutrophils and the biofilm 

target will be 

Year 1 Year 2 Year 3 Year 4

Aim 1 Activity 1 & 2 Activity 1 & 2 Activity 1 & 2

Aim 2 Activity 1 Activities 1 & 2 Activities 2 & 3 Activity 3

Aim 3 Activity 1 Activity 1 Activity 2 Activity 3

linked to a greater probability of phagocytosis [270].

Timeline:

Structure of the Collaboration: P.I. Vernita Gordon will lead the collaboration and coordinate efforts. She 

will directly supervise image analysis of biofilm structure and wound transport properties (Activities 1-1&2) and 

in vitro determination of the effects of structure on antibiotic resistance and virulence (Specific Aim 2) and the 

impact of mechanics on phagocytosis (Activities 3-1&2). Collaborator Kendra Rumbaugh will supervise animal 

work in Specific Aim 1 and Activity 3-3. Collaborator Gordon Christopher will supervise ex vivo measurements 

of biofilm mechanics in Activity 1-3. Collaborator Jason Shear will supervise μ3D-printing experiments in 

Activity 2-2. Students and senior personnel will meet in person at least yearly. Skype meetings will be held at 

least monthly. Students will prepare written reports bimonthly, for distribution to all senior personnel. Gordon 

and Rumbaugh have a joint manuscript under review at mBio.

General Methods, Scientific Rigor, and Biological Variables Criteria:

Blinded studies: the bacterial strains used will be coded so that researchers at Texas Tech (Rumbaugh, 

Christopher) will not know which strains were used until experiments and analysis are completed.

It is possible that characteristics of the mouse host, such as strain, sex, and age, may impact our 

findings. However, the focus of the present study is on characterizing bacterial behaviors and properties and it 

is outside the scope of this study to examine all the host factors that might impact this.
Contact PD/PI: Gordon, Vernita

Vertebrate Animals Page 98

VERTEBRATE ANIMALS

All experiments will be carried out in strict accordance with the recommendations in the Guide for the Care and 

Use of Laboratory Animals of the National Institutes of Health. The protocol was approved by the Institutional 

Animal Care and Use Committee of Texas Tech University Health Sciences Center (Protocol Number: 07044).

1) Description of the proposed use of animals: Adult, female, Swiss Webster mice will be used in the 

experiments proposed. Swiss Webster is a well-characterized outbred strain of white mice, which is 

susceptible to infection with ESKAPE wound pathogens (Enterococcus faecium, Staphylococcus aureus, 

Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species) and have 

been used extensively by our group. The non-lethal surgical excision mouse model will be used to study 

chronic infection as previously described.1-4 Specifically, mice will be anesthetized by intraperitoneal injection 

of sodium pentobarbital. After a surgical plane of anesthesia is reached the backs will be shaved and mice 

administered a full-thickness, dorsal, 1.0 x 1.0 cm excisional skin wound to the level of panniculus muscle with 

surgical scissors. Wounds will then be infected with approximately 105 colony forming units of bacteria and 

covered with a semipermeable polyurethane dressing (OPSITE dressing). Mice will then be given warmed 

lactated ringers as fluid replacement and allowed to recover under warming lights. The adhesive dressings 

prevent contractile healing and ensure that these wounds heal by deposition of granulation tissue, much like 

human wounds. We have shown that this infection can persist for weeks and is highly recalcitrant to antibiotic 

treatments.

2) Justify the use of animals: Although artificial skin models have been used for studying wound healing, 

there are currently no good in vitro models for evaluating the host response to wound infection. For the 

experiments described in this proposal, we will require a model that, as closely as possible, reflects the

infection sequela seen in human wound patients. Dr. Rumbaugh has over 16 years’ experience utilizing acute 

and chronic wound mouse models 2, 5-14. The numbers of animals to be used for the efficacy experiments are 

based on our experience of determining the minimum number of mice needed to generate statistically 

significant data. With our prior experience with this model, to power the study with a 85% confidence interval, a 

minimum of 9-12 animals will be needed for each experimental group (depending on the number of parameters 

being assessed). Smaller group sizes can often be used when larger effects are expected. However, until we 

know the expected variance in outcome, exact sample size estimates cannot be made. We have carefully tried 

to design the experiments so that data from as many parameters possible will be obtained from as few mice 

possible. These experiments are detailed in Table 2 of the Research Plan. In our experimental design we 

have conscientiously attempted to plan as many assays per mouse as possible.

3) Provide information on the veterinary care of the animals involved: Animals are housed in the centrally 

managed TTUHSC Animal Facility under the supervision of a staff vivarium director, a veterinarian (Dr. Scott 

Trasti), a staff of trained support personnel, which is overseen by the TTUHSC Animal Care Committee. 

TTUHSC is fully accredited by the AALAC. An Institutional Animal Care and Use Committee reviews all the 

proposals to ensure the ethical and humane treatment of animals. The vivarium follows the NIH Guide for the 

Care and Use of Laboratory Animals (revised 1985) prepared by the Institute of Laboratory Animal Resources, 

National Research Council, all applicable government regulations, and TTUHSC policies governing the care 

and use of laboratory animal. All physical plant construction, as well as plant maintenance, husbandry, and 

transportation, are in compliance with the Animal Welfare Act (PL89-544, PL91-579 and PL94-279).

4) Describe the procedures for ensuring that discomfort, distress, pain, and injury will be limited to that 

which is unavoidable in the conduct of scientifically sound research: To alleviate discomfort, distress 

and pain, after surgery and during wound care, analgesics will be given (1-2% lidocaine (max dose of 10 

mg/kg) + 0.25-0.5% bupivacaine in equal volume) twice daily (AM and PM) pre-emptively. Analgesics will also 

be given if there are signs of sickness; inactivity, sunken eyes, hunched posture, matted fur, abdominal 

vacuolization when handled. A mouse showing signs of morbidity (recumbent posture, labored breathing, 

unresponsiveness) will be euthanized. In addition, moist food within reach and additional bedding materials will 

be provided. Euthanasia is carried out by intracardial injection of ‘Fatal Plus’, a method approved by the 

American Veterinary Medical Association Panel on Euthanasia.
Contact PD/PI: Gordon, Vernita

Vertebrate Animals Page 99

5) Describe any method of euthanasia to be used and the reasons for its selection: Euthanasia is carried 

out by intracardial injection of ‘Fatal Plus’, a method approved by the AVMA Panel onEuthanasia.

Table 1. Breakdown and numbers of mice to be used

Experimental Group Data to be obtained # of mice/ 

group

# of 

repeats

# of PA 

strains

tested

# of time 

points

assessed

Total 

number of

mice

Specific Aim 1: Determine the spatial structure and mechanics of biofilm infections in chronic wounds

Activity 1.1- Determine the structures of P. aeruginosa biofilm infections as a function of infection time and matrix 

production capability

Uninfected control Bacterial load, wound 

closure/healing, spatial 

distribution

4 3 - 3 36

P. aeruginosa infection Bacterial load, wound

closure/healing

4 3 6 3 216

Activity 1.2 Determine biofilm mechanics as a function of matrix content and infection time

Uninfected control mechanics of biofilm material 

in wounds

4 3 - 3 36

P. aeruginosa infection mechanics of biofilm material 

in wounds

4 3 5 3 180

Specific Aim 3: Determine the role of mechanics and virulence in biofilm-neutrophil interactions

Uninfected, hydrogel

alone

Bacterial load, wound

closure/healing, biomarkers

4 3 - 2 24

P. aeruginosa in

hydrogel

Bacterial load, wound 

closure/healing, biomarkers

4 3 2x4 gel 

variants

2 192

Total 684

ETHICAL ASPECTS OF PROPOSED RESEARCH

We intend to use mice for experiments described in this study. We have conscientiously attempted to design 

our experiments to evaluate as many parameters per mouse as possible. Procedures to reduce discomfort, 

distress, pain, and injury have been put in place including the use of a preemptive analgesic. Mice used in 

these experiments will be treated humanely and in accordance with the protocol approved by the Animal Care 

and Use Committee at Texas Tech University Health Sciences Center (Lubbock, TX).

References for this section:

[1] Holder, I. A., Brown, R. L., Greenhalgh, D.G. (1997) Mouse models to study wound closure and topical 

treatment of infected wounds in healing-impaired and normal healing hosts, Wound Repair Regen 5, 

198-204.

[2] Rumbaugh, K. P., Diggle, S. P., Watters, C. M., Ross-Gillespie, A., Griffin, A. S., and West, S. A. (2009) 

Quorum sensing and the social evolution of bacterial virulence, Curr Biol 19, 341-345.

[3] Dalton, T., Dowd, S. E., Wolcott, R. D., Sun, Y., Watters, C., Griswold, J. A., and Rumbaugh, K. P. (2011) 

An in vivo polymicrobial biofilm wound infection model to study interspecies interactions, PLoS One 6, 

e27317.

[4] Wolcott, R. D., Rumbaugh, K. P., James, G., Schultz, G., Phillips, P., Yang, Q., Watters, C., Stewart, P. S., 

and Dowd, S. E. (2010) Biofilm maturity studies indicate sharp debridement opens a time- dependent 

therapeutic window, J Wound Care 19, 320-328.

[5] DeLeon, K., Balldin, F., Watters, C., Hamood, A., Griswold, J., Sreedharan, S., and Rumbaugh, K. P. 

(2009) Gallium maltolate treatment eradicates Pseudomonas aeruginosa infection in thermally injured 

mice, Antimicrob Agents Chemother 53, 1331-1337.

[6] Haynes, A., 3rd, Ruda, F., Oliver, J., Hamood, A. N., Griswold, J. A., Park, P. W., and Rumbaugh, K. P. 

(2005) Syndecan 1 Shedding Contributes to Pseudomonas aeruginosa Sepsis, Infect Immun 73, 7914- 

7921.

[7] Haynes, A., 3rd, Rumbaugh, K. P., Park, P. W., Hamood, A. N., and Griswold, J. A. (2005) Protamine 

sulfate reduces the susceptibility of thermally injured mice to Pseudomonas aeruginosa infection, J 

Surg Res 123, 109-117.

[8] Rashid, M. H., Rumbaugh, K., Passador, L., Davies, D. G., Hamood, A. N., Iglewski, B. H., and Kornberg,

A. (2000) Polyphosphate kinase is essential for biofilm development, quorum sensing, and virulenceof 

Pseudomonas aeruginosa, Proc Natl Acad Sci U S A 97, 9636-9641.
Contact PD/PI: Gordon, Vernita

Vertebrate Animals Page 100

[9] Rumbaugh, K. P., Colmer, J. A., Griswold, J. A., and Hamood, A. N. (2001) The effects of infection of 

thermal injury by Pseudomonas aeruginosa PAO1 on the murine cytokine response, Cytokine 16, 160- 

168.

[10] Rumbaugh, K. P., Griswold, J. A., and Hamood, A. N. (1999) Contribution of the regulatory gene lasR to 

the pathogenesis of Pseudomonas aeruginosa infection of burned mice, J Burn Care Rehabil 20, 42- 

49.

[11] Rumbaugh, K. P., Griswold, J. A., Iglewski, B. H., and Hamood, A. N. (1999) Contribution of quorum 

sensing to the virulence of Pseudomonas aeruginosa in burn wound infections, Infect Immun 67, 5854- 

5862.

[12] Rumbaugh, K. P., Hamood, A. N., and Griswold, J. A. (1999) Analysis of Pseudomonas aeruginosa clinical 

isolates for possible variations within the virulence genes exotoxin A and exoenzyme S, J Surg Res 82, 

95-105.

[13] Rumbaugh, K. P., Hamood, A. N., and Griswold, J. A. (2004) Cytokine induction by the P. aeruginosa 

quorum sensing system during thermal injury, J Surg Res 116, 137-144.

[14] Schaber, J. A., Triffo, W. J., Suh, S. J., Oliver, J. W., Hastert, M. C., Griswold, J. A., Auer, M., Hamood, A. 

N., and Rumbaugh, K. P. (2007) Pseudomonas aeruginosa Forms Biofilms in Acute Infection 

Independent of Cell-to-Cell Signaling, Infect Immun 75, 3715-3721.
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Resource Sharing Plan(s) Page 130

Resource Sharing Plan

New bacterial strains generated or harvested will be permanently stored at -80C, in replicate. 

We will make them available to other researches upon request. After publication and upon 

request, we will also share experimental protocols, software developed, and data in the form of 

microscopy movies and analysis and rheology and analysis. Protocols, software, and data will 

be shared over email or by electronic transfer; strains will be shipped at the requester’s 

expense, if pick-up in person is not practicable. Gene sequences will be deposited in the 

National Center for Biotechnology Short-Read Archive, the Pseudomonas Genome Database 

and the Sequence Read Archive. If new genetic sequences are measured, these will be stored 

as textfiles and deposited in publically-accessible repositories at the same time as any relevant 

publications. If transcriptome data is measured, it will be stored as textfiles.

Software will be stored as Matlab, IDL, or other code, as appropriate. All microscopy images 

and associated analysis are stored both in proprietary format and in open format (TIFF for 

images, TXT for analysis) on a doubly-redundent RAID system on a dedicated Linux server. 

Rheometer data and AFM force measurements will be stored in open-reading-format textfiles 

along with metadata, as well as in supported proprietary formats. ELISA, immunoblot, and platereader data will be stored as textfiles, with accompanying metadata, and redundantly recorded 

in accompanying hardcopy. Immunoblot data and the staining data acquired by microscopy will 

also be stored as tif files, with accompanying metadata, as for the micrographs above.

Additional backups are done regularly to removable external hard drives. Archival data will be 

stored on stable long-term media, currently archive grade DVD-RW. We will upgrade this as 

necessary as technology progresses, ensuring that our data are always in a readable format. In 

addition, researchers will keep careful lab notebooks with full details of experiments, so that 

experiments can be reconstructed as fully as possible even after students have graduated and 

left the group.

We will promptly prepare and submit for publication, with authorship that accurately reflects the 

contributions of those involved, all significant findings. Post-publication, we will share data and 

metadata with other researchers promptly upon request at only the incremental costs thereby 

incurred. Sufficiently-small computer files will be shared using email or network transfer, 

incurring no incremental costs. If this is not practical, data will be made available to other 

researchers on portable media, such as removable hard drive, as supplied by the requester.

Bacterial strains generated will be shipped in accordance with standard BSL-2 protocols. 

Sequences generated, if any, will be deposited in publically-accessible repositories.

. 
Contact PD/PI: Gordon, Vernita

Authentication of Key Biological and/or Chemical Resources Page 131

Authentication of Key Biological and/or Chemical Resources

Strains will be acquired from the P. aeruginosa transposon mutant libraries – we have in hand 

those strains that we intend to use in the proposed research. Strains will be authenticated using 

polymerase chain reaction (PCR) on the respective genes, for wild-type and mutant strains. 

Strains that have had a gene disrupted by transposon mutagenesis (∆ strains) will show an 

increase in the size due to the insertion of the transposon. We used this approach previously to 

authenticate strains used in our work on self-inhibition of bacteria in the presence of antibiotic 

[1].

Bacteria strains will be stored in a -80 freezer and will periodically be reisolated and checked for 

their appropriate phenotypic/antibiotic markers.

We will verify antibodies using Western blot and immunoprecipitation using EPS extracts from 

wild-type, over-expressor, and knockout strains. We used this approach previously to 

authenticate a Psl antibody and to show that it had a low degree of non-specific binding to nonPsl EPS material [2].

We will use outspread white mice for our animal model. Therefore, we will not perform any 

authentication per se on the mice, but we will closely review health monitoring reports from the 

vendor, as well as health reports from the sentinel animals in our laboratory animal facility.

We buy high-quality chemical reagents (including antibiotics) from sources such as SigmaAldrich and Invitrogen. Chemicals will be validated by checking pH, mass spectrometry, and 

confirming known biological activity (such as known minimal inhibitory concentrations of 

antibiotic for well-characterized strains of bacteria such as E. coli).

1. Kaushik, K., N. Ratnayeke, P. Katira, and V. Gordon, The spatial profiles and metabolic 

capabilities of microbial populations impact the growth of antibiotic-resistant mutants. Journal 

of the Royal Society Interface, 2015. 12: p. DOI: 10.1098/rsif.2015.0018.

2. Cooley, B., S. Dellos-Nolan, N. Dhamani, R. Todd, W. Waller, D. Wozniak, and V. Gordon, 

Asymmetry and inequity in the inheritance of a bacterial adhesive. New Journal of Physics, 2016. 

18: p. 045019.