bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amariner-Based Transposition System forListeria monocytogenes
Authors: Cao Min , Bitar Alan Pavinski , Marquis Hélène 
Published: February 2007

ABSTRACTIn this study, we developed a newmariner-based transposition system forListeria monocytogenes. Themariner-based system has a high rate of transposition and a low rate of plasmid retention, and transposition is very random, making it an ideal tool for high-throughput transposon mutagenesis inL. monocytogenes.
Fluorescence-Based Bacterial Overlay Method for Simultaneous In Situ Quantification of Surface-Attached Bacteria
Authors: Müller Rainer , Gröger Gerhard , Hiller Karl-Anton , Schmalz Gottfried , Ruhl Stefan 
Published: February 2007

ABSTRACT

For quantification of bacterial adherence to biomaterial surfaces or to other surfaces prone to biofouling, there is a need for methods that allow a comparative analysis of small material specimens. A new method for quantification of surface-attached biotinylated bacteria was established by in situ detection with fluorescence-labeled avidin-D. This method was evaluated utilizing a silicon wafer model system to monitor the influences of surface wettability and roughness on bacterial adhesion. Furthermore, the effects of protein preadsorption from serum, saliva, human serum albumin, and fibronectin were investigated.
Streptococcus gordonii
,
Streptococcus mitis
, and
Staphylococcus aureus
were chosen as model organisms because of their differing adhesion properties and their clinical relevance. To verify the results obtained by this new technique, scanning electron microscopy and agar replica plating were employed. Oxidized and poly(ethylene glycol)-modified silicon wafers were found to be more resistant to bacterial adhesion than wafers coated with hydrocarbon and fluorocarbon moieties. Roughening of the chemically modified surfaces resulted in an overall increase in bacterial attachment. Preadsorption of proteins affected bacterial adherence but did not fully abolish the influence of the original surface chemistry. However, in certain instances, mostly with saliva or serum, masking of the underlying surface chemistry became evident. The new bacterial overlay method allowed a reliable quantification of surface-attached bacteria and could hence be employed for measuring bacterial adherence on material specimens in a variety of applications.
Persistence and Decontamination of
Bacillus atrophaeus
subsp.
globigii
Spores on Corroded Iron in a Model Drinking Water System
Authors: Szabo Jeffrey G. , Rice Eugene W. , Bishop Paul L. 
Published: February 2007

ABSTRACT

Persistence of
Bacillus atrophaeus
subsp.
globigii
spores on corroded iron coupons in drinking water was studied using a biofilm annular reactor. Spores were inoculated at 10
6
CFU/ml in the dechlorinated reactor bulk water. The dechlorination allowed for observation of the effects of hydraulic shear and biofilm sloughing on persistence. Approximately 50% of the spores initially adhered to the corroded iron surface were not detected after 1 month. Addition of a stable 10 mg/liter free chlorine residual after 1 month led to a 2-log
10
reduction of adhered
B. atrophaeus
subsp.
globigii
, but levels on the coupons quickly stabilized thereafter. Increasing the free chlorine concentration to 25 or 70 mg/liter had no additional effect on inactivation.
B. atrophaeus
subsp.
globigii
spores injected in the presence of a typical distribution system chlorine residual (∼0.75 mg/liter) resulted in a steady reduction of adhered
B. atrophaeus
subsp.
globigii
over 1 month, but levels on the coupons eventually stabilized. Adding elevated chlorine levels (10, 25, and 70 mg/liter) after 1 month had no effect on the rate of inactivation. Decontamination with elevated free chlorine levels immediately after spore injection resulted in a 3-log
10
reduction within 2 weeks, but the rate of inactivation leveled off afterward. This indicates that free chlorine did not reach portions of the corroded iron surface where
B. atrophaeus
subsp.
globigii
spores had adhered.
B. atrophaeus
subsp.
globigii
spores are capable of persisting for an extended time in the presence of high levels of free chlorine.
The
Dehalococcoides
Population in Sediment-Free Mixed Cultures Metabolically Dechlorinates the Commercial Polychlorinated Biphenyl Mixture Aroclor 1260
Authors: Bedard Donna L. , Ritalahti Kirsti M. , Löffler Frank E. 
Published: February 2007

ABSTRACT

Microbial reductive dechlorination of commercial polychlorinated biphenyl (PCB) mixtures (e.g., Aroclors) in aquatic sediments is crucial to achieve detoxification. Despite extensive efforts over nearly two decades, the microorganisms responsible for Aroclor dechlorination remained elusive. Here we demonstrate that anaerobic bacteria of the
Dehalococcoides
group derived from sediment of the Housatonic River (Lenox, MA) simultaneously dechlorinate 64 PCB congeners carrying four to nine chlorines in Aroclor 1260 in the sediment-free JN cultures. Quantitative real-time PCR showed that the
Dehalococcoides
cell titer in JN cultures amended with acetate and hydrogen increased from 7.07 × 10
6
± 0.42 × 10
6
to 1.67 × 10
8
± 0.04 × 10
8
cells/ml, concomitant with a 64.2% decrease of the PCBs with six or more chlorines in Aroclor 1260. No
Dehalococcoides
growth occurred in parallel cultures without PCBs. Aroclor 1260 dechlorination supported the growth of 9.25 × 10
8
± 0.04 × 10
8
Dehalococcoides
cells per μmol of chlorine removed. 16S rRNA gene-targeted PCR analysis of known dechlorinators (i.e.,
Desulfitobacterium
,
Dehalobacter
,
Desulfuromonas
,
Sulfurospirillum
,
Anaeromyxobacter
,
Geobacter
, and
o
-17/DF-1-type
Chloroflexi
organisms) ruled out any involvement of these bacterial groups in the dechlorination. Our results suggest that the
Dehalococcoides
population present in the JN cultures also catalyzes in situ dechlorination of Aroclor 1260 in the Housatonic River. The identification of
Dehalococcoides
organisms as catalysts of extensive Aroclor 1260 dechlorination and our ability to propagate the JN cultures under defined conditions offer opportunities to study the organisms' ecophysiology, elucidate nutritional requirements, identify reductive dehalogenase genes involved in PCB dechlorination, and design molecular tools required for bioremediation applications.
Isolation and Characterization of Bacteria Capable of Tolerating the Extreme Conditions of Clean Room Environments
Authors: La Duc Myron T. , Dekas Anne , Osman Shariff , Moissl Christine , Newcombe David , Venkateswaran Kasthuri 
Published: February 2007

ABSTRACTIn assessing the bacterial populations present in spacecraft assembly, spacecraft test, and launch preparation facilities, extremophilic bacteria (requiring severe conditions for growth) and extremotolerant bacteria (tolerant to extreme conditions) were isolated. Several cultivation approaches were employed to select for and identify bacteria that not only survive the nutrient-limiting conditions of clean room environments but can also withstand even more inhospitable environmental stresses. Due to their proximity to spacefaring objects, these bacteria pose a considerable risk for forward contamination of extraterrestrial sites. Samples collected from four geographically distinct National Aeronautics and Space Administration clean rooms were challenged with UV-C irradiation, 5% hydrogen peroxide, heat shock, pH extremes (pH 3.0 and 11.0), temperature extremes (4°C to 65°C), and hypersalinity (25% NaCl) prior to and/or during cultivation as a means of selecting for extremotolerant bacteria. Culture-independent approaches were employed to measure viable microbial (ATP-based) and total bacterial (quantitative PCR-based) burdens. Intracellular ATP concentrations suggested a viable microbial presence ranging from below detection limits to 106cells/m2. However, only 0.1 to 55% of these viable cells were able to grow on defined culture medium. Isolated members of theBacillaceaefamily were more physiologically diverse than those reported in previous studies, including thermophiles (Geobacillus), obligate anaerobes (Paenibacillus), and halotolerant, alkalophilic species (OceanobacillusandExiguobacterium). Non-spore-forming microbes (α- and β-proteobacteria and actinobacteria) exhibiting tolerance to the selected stresses were also encountered. The multiassay cultivation approach employed herein enhances the current understanding of the physiological diversity of bacteria housed in these clean rooms and leads us to ponder the origin and means of translocation of thermophiles, anaerobes, and halotolerant alkalophiles into these environments.
The 29-Kilodalton Thiol-Dependent Peroxidase of
Entamoeba histolytica
Is a Factor Involved in Pathogenesis and Survival of the Parasite during Oxidative Stress
Authors: Sen Abhik , Chatterjee Nabendu Sekhar , Akbar M. Ali , Nandi Nilay , Das Pradeep 
Published: February 2007

ABSTRACT

The 29-kDa surface antigen (thiol-dependent peroxidase; Eh29) of
Entamoeba histolytica
exhibits peroxidative and protective antioxidant activities. During tissue invasion, the trophozoites are exposed to oxidative stress and need to deal with highly toxic reactive oxygen species (ROS). In this investigation, attempts have been made to understand the role of the 29-kDa peroxidase gene in parasite survival and pathogenesis. Inhibition of
eh29
gene expression by antisense RNA technology has shown approximately 55% inhibition in
eh29
expression, maximum ROS accumulation, and significantly lower viability in 29-kDa downregulated trophozoites during oxidative stress. The cytopathic and cytotoxic activities were also found to decrease effectively in the 29-kDa downregulated trophozoites. Size of liver abscesses was substantially lower in hamsters inoculated with 29-kDa downregulated trophozoites compared to the normal HM1:IMSS. These findings clearly suggest that the 29-kDa protein of
E. histolytica
has a role in both survival of trophozoites in the presence of ROS and pathogenesis of amoebiasis.
Purification of Components of the Translation Elongation Factor Complex of
Plasmodium falciparum
by Tandem Affinity Purification
Authors: Takebe Sachiko , Witola William Harold , Schimanski Bernd , Günzl Arthur , Ben Mamoun Choukri 
Published: February 2007

ABSTRACT

Plasmodium falciparum
is the causative agent of severe human malaria, responsible for over 2 million deaths annually. Of the 5,300 polypeptides predicted to control the parasite life cycle in mosquitoes and humans, 60% are of unknown function. A major challenge of malaria postgenomic biology is to understand how the 5,300 predicted proteins coexist and interact to perform the essential tasks that define the complex life cycle of the parasite. One approach to assign function to these proteins is by identifying their physiological partners. Here we describe the use of tandem affinity purification (TAP) and mass spectrometry for identification of native protein interactions and purification of protein complexes in
P. falciparum
. Transgenic parasites were generated which express the translation elongation factor PfEF-1β harboring a C-terminal PTP tag which consists of the protein C epitope, a tobacco etch virus protease cleavage site, and two protein A domains. Purification of PfEF-1β-PTP from crude extracts followed by mass spectrometric analysis revealed, in addition to the tagged protein itself, the presence of the native PfEF-1β, the G-protein PfEF-1α, and two new proteins that we named PfEF-1γ and PfEF-1δ based on their homology to other eukaryotic γ and δ translation elongation factor subunits. These data, which constitute the first application of TAP for purification of a protein complex under native conditions in
P. falciparum
, revealed that the translation elongation complex in this organism contains at least two subunits of PfEF-1β. The success of this approach will set the stage for a systematic analysis of protein interactions in this important human pathogen.
Gamma Interferon Responses of CD4 and CD8 T-Cell Subsets Are Quantitatively Different and Independent of Each Other during PulmonaryMycobacterium bovisBCG Infection
Authors: Ngai Patricia , McCormick Sarah , Small Cherrie , Zhang Xizhong , Zganiacz Anna , Aoki Naoko , Xing Zhou 
Published: February 2007

ABSTRACTGamma interferon (IFN-γ) is a key cytokine in host defense against intracellular mycobacterial infection. It has been believed that both CD4 and CD8 T cells are the primary sources of IFN-γ. However, the relative contributions of CD4 and CD8 T-cell subsets to IFN-γ production and the relationship between CD4 and CD8 T-cell activation have not been examined. By using a model of pulmonary mycobacterial infection and various immunodetection assays, we found that CD4 T cells mounted a much stronger IFN-γ response than CD8 T cells at various times after mycobacterial infection, and this pronounced IFN-γ production by CD4 T cells was attributed to both greater numbers of antigen-specific CD4 T cells and a greater IFN-γ secretion capacity of these cells. By using major histocompatibility complex class II-deficient or CD4-deficient mice, we found that the lack of CD4 T cells did not negatively affect primary or secondary CD8 T-cell IFN-γ responses. The CD8 T cells activated in the absence of CD4 T cells were capable of immune protection against secondary mycobacterial challenge. Our results suggest that, whereas both CD4 and CD8 T cells are capable of IFN-γ production, the former represent a much greater cellular source of IFN-γ. Moreover, during mycobacterial infection, CD8 T-cell IFN-γ responses and activation are independent of CD4 T-cell activation.
Enterococcus faecalis
Mutations Affecting Virulence in the
Caenorhabditis elegans
Model Host
Authors: Maadani Arash , Fox Kristina A. , Mylonakis Elftherios , Garsin Danielle A. 
Published: February 2007

ABSTRACT

Enterococcus faecalis
transposon insertion mutants were screened for attenuated killing of the nematode model host
Caenorhabditis elegans
. The genes disrupted in the attenuated mutants encode a variety of factors including transcriptional regulators, transporters, and damage control and repair systems. Five of nine mutants tested were attenuated in a mouse peritonitis model.
Chlamydial Hsp60-2 Is Iron Responsive in
Chlamydia trachomatis
Serovar E-Infected Human Endometrial Epithelial Cells In Vitro
Authors: LaRue Richard W. , Dill Brian D. , Giles David K. , Whittimore Judy D. , Raulston Jane E. 
Published: February 2007

ABSTRACT

Chlamydial 60-kDa heat shock proteins (cHsp60s) are known to play a prominent role in the immunopathogenesis of disease. It is also known that several stress-inducing growth conditions, such as heat, iron deprivation, or exposure to gamma interferon, result in the development of persistent chlamydial forms that often exhibit enhanced expression of cHsp60. We have shown previously that the expression of cHsp60 is greatly enhanced in
Chlamydia trachomatis
serovar E propagated in an iron-deficient medium. The objective of this work was to determine which single cHsp60 or combination of the three cHsp60 homologs encoded by this organism responds to iron limitation. Using monospecific polyclonal peptide antisera that recognize only cHsp60-1, cHsp60-2, or cHsp60-3, we found that expression of cHsp60-2 is responsive to iron deprivation. Overall, our studies suggest that the expression of cHsp60 homologs differs among the mechanisms currently known to induce persistence.
Identification of a Prepore Large-Complex Stage in the Mechanism of Action of
Clostridium perfringens
Enterotoxin
Authors: Smedley James G. , Uzal Francisco A. , McClane Bruce A. 
Published: February 2007

ABSTRACT

Clostridium perfringens
enterotoxin (CPE) is the etiological agent of the third most common food-borne illness in the United States. The enteropathogenic effects of CPE result from formation of large CPE-containing complexes in eukaryotic cell membranes. Formation of these ∼155- and ∼200-kDa complexes coincides with plasma membrane permeability changes in eukaryotic cells, causing a Ca
2+
influx that drives cell death pathways. CPE contains a stretch of amino acids (residues 81 to 106) that alternates markedly in side chain polarity (a pattern shared by the transmembrane domains of the β-barrel pore-forming toxin family). The goal of this study, therefore, was to investigate whether this CPE region is involved in pore formation. Complete deletion of the CPE region from 81 to 106 produced a CPE variant that was noncytotoxic for Caco-2 cells and was unable to form CPE pores. However, this variant maintained the ability to form the ∼155-kDa large complex. This large complex appears to be a prepore present on the plasma membrane surface since it showed greater susceptibility to proteases, increased complex instability, and a higher degree of dissociation from membranes compared to the large complex formed by recombinant CPE. When a D48A mutation was engineered into this prepore-forming CPE variant, the resultant variant was unable to form any prepore ∼155-kDa large complex. Collectively these findings reveal a new step in CPE action, whereby receptor binding is followed by formation of a prepore large complex, which then inserts into membranes to form a pore.
Primary Infection of C57BL/6 Mice withPlasmodium yoeliiInduces a Heterogeneous Response of NKT Cells
Authors: Soulard Valérie , Roland Jacques , Sellier Christèle , Gruner Anne Charlotte , Leite-de-Moraes Maria , Franetich Jean-François , Rénia Laurent , Cazenave Pierre-André , Pied Sylviane 
Published: February 2007

ABSTRACTNKT cells are a population of innate-like lymphocytes that display effector functions and immunoregulatory properties. We characterized the NKT cell response induced in C57BL/6 mice during a primary infection withPlasmodium yoeliisporozoites. We observed a heterogeneous NKT cell response that differed between liver and spleen. Hepatic NKT cells found in infected livers consisted mainly of CD1d-dependent CD4+and double-negative (DN) NKT cells, whereas CD1d-independent NKT cells exhibiting a TCRhighCD4highphenotype were prominent among splenic NKT cells during the infection. Hepatic and splenic NKT cells isolated from infected mice were activated and secreted mainly gamma interferon and tumor necrosis factor alpha in response to stimulation. Finally,P. yoelii-activated hepatic DN NKT cells inhibited the parasite's liver stage in a CD1d-dependent manner in vitro. However, experiments using B6.CD1d-deficient mice showed that CD1d and CD1d-restricted NKT cells are not necessary to control the parasite's development in vivo during neither the preerythrocytic stage nor the erythrocytic stage. Thus, our results show that a primaryP. yoeliiinfection induces a heterogeneous and organ-specific response of NKT cells and that CD1d-dependent NKT cells play a minor role in the control of the development ofPlasmodiumin vivo in our model.
The
Escherichia coli
Enterotoxin STb Permeabilizes Piglet Jejunal Brush Border Membrane Vesicles
Authors: Gonçalves Carina , Vachon Vincent , Schwartz Jean-Louis , Dubreuil J. Daniel 
Published: February 2007

ABSTRACT

The membrane-permeabilizing ability of the
Escherichia coli
enterotoxin STb was evaluated using brush border membrane vesicles isolated from piglet jejunum and a membrane-potential-sensitive fluorescent probe, 3,3′-dipropylthiadicarbocyanine iodide. A strong membrane potential was generated by the efflux of K
+
ions from the vesicles in the presence of the potassium ionophore valinomycin. Under these conditions, preincubation of the vesicles with STb efficiently depolarized the membrane in a dose-dependent and saturable manner. This activity was independent of pH, however, at least between pH 5.5 and 8.0. On the other hand, in the absence of valinomycin, STb had no significant influence on the measured fluorescence levels, indicating that it was unable to modify the ionic selectivity of the intact membrane. In agreement with the fact that the integrity of the disulfide bridges of STb is known to be essential for its biological activity, a reduced and alkylated form of the toxin was unable to depolarize the membrane in the presence of valinomycin. Furthermore, two previously described poorly active STb mutants, M42S and K22A-K23A, showed no membrane-permeabilizing capacity. These results demonstrate for the first time that STb can permeabilize its target membrane and suggest that it does so by forming nonspecific pores.
Gamma Interferon Suppresses Erythropoiesis via Interleukin-15
Authors: Mullarky Isis K. , Szaba Frank M. , Kummer Lawrence W. , Wilhelm Lindsey B. , Parent Michelle A. , Johnson Lawrence L. , Smiley Stephen T. 
Published: February 2007

ABSTRACTImpaired erythropoiesis causes anemia during genetic disorders, chronic disease, and infection. In studies of the underlying mechanisms researchers have increasingly focused on gamma interferon (IFN-γ). Here, we identified a previously unrecognized role for interleukin-15 (IL-15) in red blood cell homeostasis and demonstrated that IFN-γ and signal transducer and activator of transcription protein 1-dependent pathways up-regulate expression of IL-15 in vivo. These findings identified new therapeutic targets for anemia.
Priming with an Adenovirus 35-Circumsporozoite Protein (CS) Vaccine followed by RTS,S/AS01B Boosting Significantly Improves Immunogenicity toPlasmodium falciparumCS Compared to That with Either Malaria Vaccine Alone
Authors: Stewart V. Ann , McGrath Shannon M. , Dubois Patrice M. , Pau Maria G. , Mettens Pascal , Shott Joseph , Cobb Michelle , Burge J. Robert , Larson David , Ware Lisa A. , Demoitie Marie-Ange , Weverling Gerrit Jan , Bayat Babak , Custers Jerome H. H. V. , Dubois Marie-Claude , Cohen Joe , Goudsmit Jaap , Heppner D. Gray 
Published: February 2007

ABSTRACTThe RTS,S/AS02A protein-based vaccine consistently demonstrates significant protection against infection withPlasmodium falciparummalaria and also against clinical malaria and severe disease in children in areas of endemicity. Here we demonstrate with rhesus macaques that priming with a replication-defective human adenovirus serotype 35 (Ad35) vector encoding circumsporozoite protein (CS) (Ad35.CS), followed by boosting with RTS,S in an improved MPL- and QS21-based adjuvant formulation, AS01B, maintains antibody responses and dramatically increases levels of T cells producing gamma interferon and other Th1 cytokines in response to CS peptides. The increased T-cell responses induced by the combination of Ad35.CS and RTS,S/AS01B are sustained for at least 6 months postvaccination and may translate to improved and more durable protection againstP. falciparuminfection in humans.