bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA prime–protein boost strategies protect cattle from bovine viral diarrhea virus type 2 challenge
Authors: Liang R. , van den Hurk J. V. , Landi A. , Lawman Z. , Deregt D. , Townsend H. , Babiuk L. A. , van Drunen Littel-van den Hurk S.
Published: January 2008

At present, infections with bovine viral diarrhea virus (BVDV) type 2 occur nearly as frequently as those with BVDV type 1, so development of vaccines that protect cattle from both type 1 and type 2 BVDV has become critical. In this study, we compared various DNA prime–protein boost vaccination strategies to protect cattle from challenge with BVDV-2 using the major protective antigen of BVDV, glycoprotein E2. Calves were immunized with a plasmid encoding either type 1 E2 (E2.1) or type 2 E2 (E2.2) or with both plasmids (E2.1+E2.2). This was followed by a heterologous boost with E2.1, E2.2 or E2.1 and E2.2 protein formulated with Emulsigen and a CpG oligodeoxynucleotide. Subsequently, the calves were challenged with BVDV-2 strain 1373. All vaccinated calves developed both humoral and cell-mediated immune responses, including virus-neutralizing antibodies and IFN-γ-secreting cells in the peripheral blood. Depletion studies showed that CD4+T cells were responsible for IFN-γproduction. Furthermore, the calves vaccinated with either the E2.2 or the E2.1+E2.2 vaccines were very well protected from challenge with BVDV-2, having little leukopenia and showing no weight loss or temperature response. In addition, the animals vaccinated with the E2.1 vaccine were partially protected, so there was a certain level of cross-protection. These data demonstrate that a vaccination strategy consisting of priming with E2.2 or E2.1+E2.2 DNA and boosting with E2.2 or E2.1+E2.2 protein fully protects cattle from BVDV-2 challenge.
Molecular characterization of occult hepatitis B virus in genotype E-infected subjects
Authors: Zahn Astrid , Li Chengyao , Danso Kwabena , Candotti Daniel , Owusu-Ofori Shirley , Temple Jillian , Allain Jean-Pierre
Published: January 2008

Occult hepatitis B virus (HBV) infection (OBI), defined as the presence of HBV DNA without detectable HBV surface antigen (HBsAg), is frequent in west Africa, where genotype E is prevalent. The prevalence of OBI in 804 blood donors and 1368 pregnant women was 1.7 and 1.5 %, respectively. Nine of 32 OBI carriers were evaluated with HBV serology, viral load and complete HBV genome sequence of two to five clones. All samples except one were anti-HBV core antigen-positive and three contained antibodies against HBsAg (anti-HBs). All strains were of genotype E and formed quasispecies with 0.20–1.28 % intra-sample sequence variation. Few uncommon mutations (absent in 23 genotype E reference sequences) were found across the entire genome. Two mutations in the core region encoded truncated or abnormal capsid protein, potentially affecting viral production, but were probably rescued by non-mutated variants, as found in one clone. No evidence of escape mutants was found in anti-HBs-carrying samples, as the ‘a’ region was consistently wild type. OBI carriers constitute approximately 10 % of all HBV DNA-viraemic adult Ghanaians. OBI carriers appear as a disparate group, with a very low viral load in common, but multiple origins reflecting decades of natural evolution in an area essentially devoid of human intervention.
Activation of the Indole-3-Acetic Acid–Amido Synthetase GH3-8 Suppresses Expansin Expression and Promotes Salicylate- and Jasmonate-Independent Basal Immunity in Rice
Authors: Ding Xinhua , Cao Yinglong , Huang Liling , Zhao Jing , Xu Caiguo , Li Xianghua , Wang Shiping
Published: January 2008

New evidence suggests a role for the plant growth hormone auxin in pathogenesis and disease resistance. Bacterial infection induces the accumulation of indole-3-acetic acid (IAA), the major type of auxin, in rice (Oryza sativa). IAA induces the expression of expansins, proteins that loosen the cell wall. Loosening the cell wall is key for plant growth but may also make the plant vulnerable to biotic intruders. Here, we report that rice GH3-8, an auxin-responsive gene functioning in auxin-dependent development, activates disease resistance in a salicylic acid signaling– and jasmonic acid signaling–independent pathway. GH3-8 encodes an IAA–amino synthetase that prevents free IAA accumulation. Overexpression of GH3-8 results in enhanced disease resistance to the rice pathogen Xanthomonas oryzae pv oryzae. This resistance is independent of jasmonic acid and salicylic acid signaling. Overexpression of GH3-8 also causes abnormal plant morphology and retarded growth and development. Both enhanced resistance and abnormal development may be caused by inhibition of the expression of expansins via suppressed auxin signaling.
Employee responses to acquisitions: evidence from Greek firms
Authors: Nikandrou Irene , Papalexandris Nancy
Published: January 2008

Purpose

The purpose of this paper is to examine the factors affecting the course of action that employees in acquired firms choose to follow. Loyalty, compliance, voice and neglect (LCVN) are four employee behaviors in acquired companies.

Design/methodology/approach

Two questionnaires were designed: one was administered to employees of the acquired company and the other to a member of the post‐acquisition managerial team. One hundred and thirty‐five administrative employees in 27 acquired companies in Greece participated in the research.

Findings

The results of the study support that employees decide their course of action based on the cost of their action, the effectiveness of the behaviour and the attractiveness of the company.

Research limitations/implications

This study concentrated at the individual level to examine the factors affecting employee behaviours. Future research is needed to examine behavioural changes over time and the factors that make employees move from one behavioural category to the other.

Practical implications

The findings in the paper have implications for organization members facing the challenge of managing human issues in the sensitive phases of an acquisition. Evidence of specific behavioural responses and the factors affecting them is presented.

Originality/value

The present study provides a model for understanding the complex and multiple behavioral choices employees have after an acquisition.
Contributions of self and organisational efficacy expectations to commitment
Authors: van Vuuren Mark , de Jong Menno D.T. , Seydel Erwin R.
Published: January 2008

Purpose

The purpose of the paper is to investigate the main and combined effects of self‐efficacy and organisational efficacy on three dimensions of organisational commitment. A fourfold typology of employees is proposed and tested.

Design/methodology/approach

A questionnaire was sent to employees of a chemical plant. Data were analyzed using dichotomisation and moderated multiple regression.

Findings

Both organisational efficacy and, to a lesser extent, self‐efficacy contribute to affective, normative and continuance commitment. The results concerning the fourfold typology are promising when reviewing the median split technique, but a hierarchical multiple regression test of interaction between self‐efficacy and organisational efficacy does not fulfil this promise.

Research limitations/implications

As the self‐efficacy hypotheses especially did not meet expectations, the authors suggest another way of assessing self‐efficacy in organisational contexts.

Practical implications

The results stress the contribution of organisational efficacy perceptions to commitment, leading to new opportunities for managing commitment. The role of feedback about organisational successes and failures appears to be crucial.

Originality/value

This attempt to build a typology by considering the efficacy expectations of employees regarding both themselves and their organisation opens up a route to further individualisation of employees and their relations to work.
Theory, research, and practice in library management 4: creativity
Authors: Walton Graham
Published: January 2008

Purpose

The purpose of this paper is to explore the relevance of creativity in the strategic management of libraries.

Design/methodology/approach

The literature is examined to show how libraries are using creativity in service development. There is also an exploration of various perspectives on creativity from both library commentators and management academics. Different approaches open to library managers to introduce creativity are examined.

Findings

The paper finds that creativity is an approach that will inform libraries develop new services in a world where turbulent change is present. Library staff should be encouraged to bring in ideas and intelligence from outside. Teams have to be made up of people with different skills and ideas and they need to be encouraged to be creative. The library manager also has to take responsibility for supporting creativity and various actions are available to him/her. These include allowing staff freedom to make decisions and making sure the work place is as stimulating as possible.

Originality/value

The paper provides food for thought for library practitioners in the use of creativity in developing future services
A 20‐year view of trying to develop emotional, social and cognitive intelligence competencies in graduate management education
Authors: Boyatzis Richard E. , Saatcioglu Argun
Published: January 2008

Purpose

Development of competencies needed to be effective managers and leaders requires program design and teaching methods focused on learning. The paper presents an update and a view of 20 years of attempting to develop these competencies.

Design/methodology/approach

A total of 14 longitudinal studies of the impact of a particular MBA program on developing emotional, social and cognitive intelligence competencies are reviewed. Three new studies are to complete a 20‐year perspective. This is a value added design. It asks how are the graduates different from when they entered the program?

Findings

Emotional, social and cognitive intelligence competencies that predict effectiveness in management and leadership can be developed in adults through a graduate management program. These improvements can sustain out as far as seven years. But this degree of value added can be eroded by a tumultuous organizational climate.

Research limitations/implications

It is a series of 17 longitudinal studies on one school. With support from four studies of a program for 45‐65 year‐old executives.

Practical implications

Competencies needed to be effective can be developed. But that development can be eroded without continuous improvement and renewal.

Originality/value

Few sets of multiyear, multi‐cohort, multi‐method, multitrait studies exist. This helps to build a new literature on learning and development, as well as focusing on development of competencies.
The impact of social environments on emotional, social, and cognitive competency development
Authors: Wheeler Jane V.
Published: January 2008

Purpose

The purpose of this research is to examine the interactions between individuals and the social environment as individuals engage in self‐directed learning, a predecessor to intentional change theory. The individuals are graduates of a part‐time MBA program and the social environment is the life sphere framework introduced with this study. Self‐directed learning refers to the learning agendas that these people outlined for themselves when they first entered the MBA program.

Design/methodology/approach

Longitudinal assessment data were collected using the critical incident interview, the learning skills profile, and the life sphere interview. Correlations were run testing the hypotheses: as the number of life spheres, relationships, or activities increases, so will the demonstration of the targeted competencies; and if the participant is able to work on developing these competencies in the life sphere that he or she designates as primary to the learning goal, then the demonstration of these competencies will improve.

Findings

The number of life spheres, relationships, and activities does impact positively on the demonstration of these competencies and those participants for whom the work organization life sphere is primary to learning goal achievement showed improved demonstration of the targeted competencies.

Research limitations/implications

The study needs to be replicated with a larger sample size. This initial study was merely exploratory in nature.

Originality/value

As society approaches the virtual office it makes sense that it will get what it needs, when it needs it – no matter where one is or to whom one is talking. With these changes has come the need to find resources in places and from people that may not have been considered previously. The relationships and activities in one's social environment are more critical than ever before.
The beat and rhythm of competency development over two years
Authors: Rhee Kenneth S.
Published: January 2008

Purpose

The purpose of this paper is to show that research supports competencies can be developed in adults; however, even in these “model programs” for developing emotional intelligence and social intelligence competencies, little is known about what goes on inside the “black box” of change. How does the change occur?

Design/methodology/approach

In an attempt to help adults develop emotional, social, and cognitive intelligence competencies, the model of intentional change theory was applied during the first of the required courses, entitled Leadership Assessment and Development in the Master of Business Administration program at Weatherhead School of Management, Case Western Reserve University. About 26 students in the program were solicited to participate in the longitudinal study, where they were assessed periodically for competency development (about six to eight weeks) during their two‐year program.

Findings

The results indicated that certain type of competencies were developed much earlier in the program (e.g. technology and quantitative), while other competencies were developed during the summer break (e.g. help and relationships) or toward the end of the program (e.g. informational analysis, theory, and goals and action). Students' career aspiration also had an impact on the rhythm and flow of competency development – while career changers steadily improved throughout the program, career explorers had spurts of improvement throughout the program, indicating their uncertain pattern of development. Overall, students' opportunity mode and desire for continuous learning significantly impacted their competency development.

Originality/value

The study raised certain implications for competency development. The relationship between opportunity utilization and intentional change – how to maximize given opportunities while seeking out new and noble opportunities – raised a question about how to structure formal competency development in organizations, especially when it comes to one's professional development. The study could not infer the underlying causal relationships between competency acquisition, program structure, subject content and initial competency demonstration level, given the limited sample size and the exploratory nature of the study.
Graph theoretical implementation of memetic algorithms in structural optimization of frame bracing layouts
Authors: Kaveh A. , Shahrouzi M.
Published: January 2008

Purpose

The generality of the genetic search in the light of proper coding schemes, together with its non‐gradient‐based search, has made it popular for many discrete problems including structural optimization. However, the required computational effort increases as the cardinality of the search space and the number of design variables increase. Memetic algorithms are formal attempts to reduce such a drawback for real‐world problems incorporating some kind of problem‐specific information. This paper aims to address this issue.

Design/methodology/approach

In this paper both Lamarckian and Baldwinian approaches for meme evolution are implemented using the power of graph theory in topology assessment. For this purpose, the concept of load path connectivity in frame bracing layouts is introduced and utilized by the proposed graph theoretical algorithms. As an additional search refinement tool, a dynamic mutation band control is recommended. In each case, the results are studied via a set of ultimate design family rather than one pseudo optimum. The method is further tested using a number of steel frame examples and its efficiency is compared with conventional genetic search.

Findings

Here, the problem of bracing layout optimization in steel frames is studied utilizing a number of topological guidelines.

Originality/value

The method of this paper attempts to reduce the computational effort for optimal design of real‐world problems incorporating some kind of problem‐specific information.
Application of geographic information system to the allocation of disaster shelters via fuzzy models
Authors: Tsai Chung‐Hung , Chen Cheng‐Wu , Chiang Wei‐Ling , Lin Meng‐Lung
Published: January 2008

Purpose

Fuzzy theory provides a rigorous, flexible approach to the problem of defining and computing. Therefore, to facilitate decision making in a geographic information system (GIS), the graph layer indicator and the Takagi‐Sugeno (T‐S) fuzzy model must be integrated. This study aims to explain several versions of the T‐S fuzzy model based on fuzzy theory and fuzzy operation.

Design/methodology/approach

An inference model is constructed for GIS using the T‐S fuzzy model to formulate an integrated T‐S decision‐making (TSDMK) system.

Findings

The TSDMK system accommodates inexact, linguistic, vague and uncertain GIS data. The operator assigns most graph layer indicators by intuition.

Practical implications

Simulation results for the Hualien main station show that the proposed TSDMK system is an effective approach for GIS decision making.

Originality/value

This investigation assesses applications of fuzzy logic for decision making in a GIS based on TSDMK graphs focusing on model‐based systems.
An analysis of advance fee fraud on the internet
Authors: Chang Joshua J.S.
Published: January 2008

Purpose

Advance fee fraud on the internet is a current epidemic that rakes in hundreds of millions of dollars per year. The advent of the internet and proliferation of its use in the 1990s makes it an attractive medium for communicating the fraud, enabling a worldwide reach. This paper aims to explain how advance fee fraud operates, to examine various cases of recent advance fee‐fraud e‐mails, and to identify methods employed to manipulate victims into compliance based on theory in human behaviour and persuasion.

Design/methodology/approach

This study uses six cases of advance fee fraud received via e‐mail by the author between August 2006 and January 2007. The content of these e‐mails was analysed in detail to identify the methods employed to manipulate the behaviour of victims.

Findings

Interpretive findings suggest that advance fee fraudsters employ specific methods that exploit the bounded rationality and automatic behaviour of victims. Methods include assertion of authority and expert power, mimicking and referencing persons/organisations, providing partial proof/legitimacy, reasoning, reciprocation, creating urgency, and implying scarcity.

Practical implications

While there is readily available information on advance fee fraud on the internet, especially in the web sites of anti‐fraud organisations, this study suggests a need to inform internet users of the methods employed by advance fee fraudsters.

Originality/value

Considering the current and widespread problem of advance fee‐fraud e‐mails, the information of this paper is important for internet users to improve their capability in identifying fraudulent schemes and avoiding them.
The distributed team members' explanations of knowledge they assume to be shared
Authors: Leinonen Piritta , Bluemink Johanna
Published: January 2008

Purpose

Evaluation of the knowledge that is shared among team members has been found to be a prerequisite for successful collaborative teamwork. In previous research on collaborative learning and work, shared knowledge has mainly been evaluated by researchers, and an individual's own perspective has been omitted. In this study the aim was to investigate how members of a distributed team explain knowledge that they assume to be shared and how an assessment tendency is related to these explanations.

Design/methodology/approach

Two distributed teams worked for two months to solve project tasks that demanded discussions and generating new ideas. Subjective explanations of their shared knowledge were studied by means of stimulated recall interviews. The concept of assessment tendency was employed to understand the differences in these explanations. Team members' assessment tendencies were examined with the assessment scale questionnaire.

Findings

Qualitative content analyses of interviews showed that explanations of shared knowledge did not focus only on contents or the outcomes of the project tasks. Instead, the distributed team members presumed their shared knowledge in terms of common goals and collaborative working processes. These evaluations were related to the outcomes of the teams. In addition, the results showed those who were proficient at assessment strategies stressed collaborative working as a shared construction process and they aimed for creation of new knowledge.

Practical implications

Interpersonal evaluation of shared knowledge is especially needed to support distributed collaborative work. However, instead of focusing on sharing and managing documents, more attention should be paid to sharing of social processes, such as setting a common goal.

Originality/value

In this paper shared knowledge is conceptualised as knowledge which is developed through situated interrelations between individuals.
EU Banking Directives: risk and wealth effects on the Greek financial sector
Authors: Pantos Themis D.
Published: January 2008

Purpose

The paper seeks to examine whether or not wealth effects and changes in the systematic risk associated with the return structure of the Greek commercial chartered banks, investment firms and insurance companies resulted from the passage of the European Union Banking Directives over the period 1988‐1997.

Design/methodology/approach

Using monthly stock returns from the DataStream database for the period January 1988 to December 1997, the separate effects of each of the EU Banking Directives on Greek commercial chartered banks, investment firms and insurance companies are tested. The “seemingly unrelated regression” methodology is utilized to test three portfolios consisting of an equally weighted banking, investment and insurance index made up of major Greek banks, investment firms and insurance companies respectively. The Greek Market Index serves as a proxy for the market portfolio. All the aforementioned indices were converted to returns using the log difference method.

Findings

Empirical results indicate that the systematic risk dramatically increased for Greek insurance and investment firms and moderately increased for Greek commercial chartered banks through the tabling of the Free Capital Movement Directive in the Greek Parliament. After controlling for systematic risk, the results suggest that the passage of the Free Capital Movement Directive did not create wealth effects for the shareholders of commercial chartered banks, investment firms and insurance companies. Conversely, the results demonstrate that the Second Banking, Investment Services and Capital Adequacy Directives produced no wealth effects for the investment firms and insurance companies, but not for commercial chartered banks' shareholders. The whole wealth effect on the Greek financial sector was neutral.

Originality/value

This article will be of value to academics, bankers, bank regulators, practitioners, and economic policy makers who are interested in the regulatory evolution of the EU banking industry.
Co‐localization of angiotensin‐converting enzyme 2‐, octomer‐4‐ and CD34‐positive cells in rabbit atherosclerotic plaques
Authors: Zulli Anthony , Rai Sudarshan , Buxton Brian F. , Burrell Louise M. , Hare David L.
Published: January 2008

Angiotensin‐converting enzyme 2 (ACE2) is a novel enzyme with possible implications in the treatment of blood pressure disorders. Recent evidence suggests that an upregulation of ACE2 can be stimulated by all‐trans retinoic acid (at‐RA); however, at‐RA also affects regulation of the stem‐cell marker octomer‐4 (Oct‐4) and thus cellular differentiation. We have previously shown that smooth muscle cells and macrophages present within rabbit atherosclerotic plaques are positive for ACE2, Oct‐4 and the haematopoietic stem‐cell marker CD34. Thus, to provide evidence that possible at‐RA treatment could affect both plaque cellular biology (via effects on cellular differentiation) and blood pressure (via ACE2), it is vital to show that cells with atherosclerotic plaques co‐express all three markers. Thus, we sought to provide evidence that a subset of cells within atherosclerotic plaques is positive for ACE2, Oct‐4 and CD34. We used New Zealand White rabbits that were fed a control diet supplemented with 0.5% cholesterol plus 1% methionine for 4 weeks and then allowed to consume a normal diet for 10 weeks. Immunohistochemistry was performed by standard techniques. We report that ACE2, Oct‐4 and CD34 were all present within atherosclerotic plaques. Although macrophages were positive for all three markers, spindle‐shaped cells in the media did not show all three markers. The endothelium overlying normal arterial wall showed positive Oct‐4 and ACE2 immunoreactivity, but CD34 immunoreactivity was patchy, indicating that such cells might not have fully differentiated. It is concluded that cells in atherosclerotic plaques express co‐express ACE2, Oct‐4 and CD34. Further studies aimed at establishing the effects of all‐trans retinoic acid on blood pressure and atherosclerotic cell differentiation are warranted.
Angiotensin‐(1–7) has a dual role on growth‐promoting signalling pathways in rat heart in vivo by stimulating STAT3 and STAT5a/b phosphorylation and inhibiting angiotensin II‐stimulated ERK1/2 and Rho kinase activity
Authors: Giani Jorge F. , Gironacci Mariela M. , Muñoz Marina C. , Turyn Daniel , Dominici Fernando P.
Published: January 2008

Angiotensin (ANG) II contributes to cardiac remodelling by inducing the activation of several signalling molecules, including ERK1/2, Rho kinase and members of the STAT family of proteins. Angiotensin‐(1–7) is produced in the heart and inhibits the proliferative actions of ANG II, although the mechanisms of this inhibition are poorly understood. Accordingly, in the present study we examined whether ANG‐(1–7) affects the ANG II‐mediated activation of ERK1/2 and Rho kinase, STAT3 and STAT5a/b in rat heart in vivo. We hypothesized that ANG‐(1–7) inhibits these growth‐promoting pathways, counterbalancing the trophic action of ANG II. Solutions of normal saline (0.9% NaCl) containing ANG II (8 pmol kg−1) plus ANG‐(1–7) in increasing doses (from 0.08 to 800 pmol kg−1) were administered via the inferior vena cava to anaesthetized male Sprague–Dawley rats. After 5 min, hearts were removed and ERK1/2, Rho kinase, STAT3 and STAT5a/b phosphorylation was determined by Western blotting using phosphospecific antibodies. Angiotensin II stimulated ERK1/2 and Rho kinase phosphorylation (2.3 ± 0.2‐ and 2.1 ± 0.2‐fold increase over basal values, respectively), while ANG‐(1–7) was without effect. The ANG II‐mediated phosphorylation of ERK1/2 and Rho kinase was prevented in a dose‐dependent manner by ANG‐(1–7) and disappeared in the presence of the Mas receptor antagonist d‐Ala7‐ANG‐(1–7). Both ANG II and ANG‐(1–7) increased STAT3 and STAT5a/b phosphorylation to a similar extent (130–140% increase). The ANG‐(1–7)‐stimulated STAT phosphorylation was blocked by the AT1 receptor antagonist losartan and not by d‐Ala7‐ANG‐(1–7). Our results show a dual action of ANG‐(1–7), that is, a stimulatory effect on STAT3 and 5a/b phosphorylation through AT1 receptors and a blocking action on ANG II‐stimulated ERK1/2 and Rho kinase phosphorylation through Mas receptor activation. The latter effect could be representative of a mechanism for a protective role of ANG‐(1–7) in the heart by counteracting the effects of locally generated ANG II.
Did Berkeley foreshadow Mach?
Authors: Newburgh Ronald
Published: January 2008

In a recent paper I discussed Mach’s rejection of Newtonian absolute space and motion and the role of Mach’s principle in relating the fixed stars to the source of inertia. The importance of Mach in Einstein’s development of the theory cannot be denied even though he later abandoned Mach’s principle. One hundred fifty years earlier Bishop Berkeley had also rejected Newton’s notions of absolute space and motion. I discuss the reason why I did not include Berkeley’s criticism of Newtonian absolute space in my recent paper.
The wave-particle duality of light: A demonstration experiment
Authors: Dimitrova T. L. , Weis A.
Published: January 2008

The wave-particle duality of light plays a fundamental role in introductory courses on quantum mechanics. Traditionally the wave and particle aspects of light are demonstrated in separate experiments which makes it difficult for students to understand their complementary nature. We present an experiment using a single apparatus that demonstrates the wave aspect, the particle aspect, and most importantly, their coexistence. The apparatus is based on a Mach-Zehnder interferometer in which a light beam is attenuated so that at each instant there is only a single photon in the interferometer. In this way the observation of single photon interference becomes possible. By integrating the single photon events in a storage oscilloscope the evolution toward classical interference fringes can be shown in real time. A second strong laser beam, derived from the same pointer, but slightly displaced, traverses the interferometer at the same time, allowing the simultaneous demonstration of wave aspects. Special features of the setup are low cost, simplicity, didactical power and suitability for presentations in large lecture halls using both multimedia projections and audible signals.
Concerning “hidden momentum”
Authors: Boyer Timothy H.
Published: January 2008

The concept of “hidden momentum” needs to be treated with care. An example of its misuse is given.
Demonstration of Allelic Exchange in the Slow-Growing Bacterium
Mycobacterium avium
subsp.
paratuberculosis
, and Generation of Mutants with Deletions at the
pknG, relA
, and
lsr2
Loci
Authors: Park Kun Taek , Dahl John L. , Bannantine John P. , Barletta Raúl G. , Ahn Jongsam , Allen Andrew J. , Hamilton Mary Jo , Davis William C.
Published: January 2008

Mycobacterium avium
subsp.
paratuberculosis
is the causative pathogen of Johne's disease, a chronic inflammatory wasting disease in ruminants. This disease has been difficult to control because of the lack of an effective vaccine. To address this need, we adapted a specialized transduction system originally developed for
M. tuberculosis
and modified it to improve the efficiency of allelic exchange in order to generate site-directed mutations in preselected
M. avium
subsp.
paratuberculosis
genes. With our novel optimized method, the allelic exchange frequency was 78 to 100% and the transduction frequency was 1.1 × 10
−7
to 2.9 × 10
−7
. Three genes were selected for mutagenesis:
pknG
and
relA
, which are genes that are known to be important virulence factors in
M. tuberculosis
and
M. bovis
, and
lsr2
, a gene regulating lipid biosynthesis and antibiotic resistance. Mutants were successfully generated with a virulent strain of
M. avium
subsp.
paratuberculosis
(
M. avium
subsp.
paratuberculosis
K10) and with a recombinant K10 strain expressing the green fluorescent protein gene,
gfp
. The improved efficiency of disruption of selected genes in
M. avium
subsp.
paratuberculosis
should accelerate development of additional mutants for vaccine testing and functional studies.
Identification of Genes Affecting Hydrogen Sulfide Formation inSaccharomyces cerevisiae
Authors: Linderholm Angela L. , Findleton Carrie L. , Kumar Gagandeep , Hong Yeun , Bisson Linda F.
Published: January 2008

A screen of theSaccharomyces cerevisiaedeletion strain set was performed to identify genes affecting hydrogen sulfide (H2S) production. Mutants were screened using two assays: colony color on BiGGY agar, which detects the basal level of sulfite reductase activity, and production of H2S in a synthetic juice medium using lead acetate detection of free sulfide in the headspace. A total of 88 mutants produced darker colony colors than the parental strain, and 4 produced colonies significantly lighter in color. There was no correlation between the appearance of a dark colony color on BiGGY agar and H2S production in synthetic juice media. Sixteen null mutations were identified as leading to the production of increased levels of H2S in synthetic juice using the headspace analysis assay. All 16 mutants also produced H2S in actual juices. Five of these genes encode proteins involved in sulfur containing amino acid or precursor biosynthesis and are directly associated with the sulfate assimilation pathway. The remaining genes encode proteins involved in a variety of cellular activities, including cell membrane integrity, cell energy regulation and balance, or other metabolic functions. The levels of hydrogen sulfide production of each of the 16 strains varied in response to nutritional conditions. In most cases, creation of multiple deletions of the 16 mutations in the same strain did not lead to a further increase in H2S production, instead often resulting in decreased levels.
Teichoic Acid Glycosylation Mediated by
gtcA
Is Required for Phage Adsorption and Susceptibility of
Listeria monocytogenes
Serotype 4b
Authors: Cheng Ying , Promadej Nattawan , Kim Jae-Won , Kathariou S.
Published: January 2008

An insertion mutant of
gtcA
, responsible for serotype-specific glycosylation of the cell wall teichoic acid in serotype 4b strains of
Listeria monocytogenes
, was also resistant to both
Listeria
genus- and serotype 4b-specific phages. The sugar substituents on teichoic acid appeared essential for the adsorption of phages A500 (serotype 4b specific) and A511 (
Listeria
genus specific) to serotype 4b
L. monocytogenes
.
Surface Response of Fluorine Polymer-Incorporated Resin Composites to Cariogenic Biofilm Adherence
Authors: Gyo Mariko , Nikaido Toru , Okada Koichi , Yamauchi Junichi , Tagami Junji , Matin Khairul
Published: January 2008

Experimental resin composites with incorporated polytetrafluoroethylene (PTFE) particles were developed, which theoretically could improve the surface properties of the materials, including the inhibition of bacterial adherence. To assess the surface properties in relation to biofilm formation and detachment, 23.1% (wt/wt) linear PTFE particles (FL-30) and cross-linked PTFE particles (FC-30) were incorporated into pure resin composites. Pure PTFE plates and pure resin composites without PTFE (F-0) were used as control specimens. Sucrose-dependent
Streptococcus mutans
biofilms were formed on the specimen blocks inside an oral biofilm reactor for various time periods and analyzed with or without application of driving forces. In addition, water contact angles and surface roughness were measured. The water contact angles of FL-30 (61.2°) and FC-30 (65.8°) were larger than that of F-0 (48.5°). The largest contact angle (107°) was detected on pure PTFE plates. However, the surfaces of FL-30, FC-30, and pure PTFE plates were rougher than that of F-0. Although the surface properties of the materials differed in terms of contact angles and roughness, these factors seemed not to affect biofilm formation on the surfaces within 5 h. Pure PTFE plates harbored almost the same amounts of biofilm as F-0. However, when a very strong driving force was applied, it was clear that there were significantly smaller amounts of biofilms retained on pure PTFE plates, which showed contact angles much higher than those of the other materials. Hydrophobicity of the resin composite was improved by incorporation of PTFE fillers. However, surface resistance against biofilm formation was not improved.
Silver as a Residual Disinfectant To Prevent Biofilm Formation in Water Distribution Systems
Authors: Silvestry-Rodriguez Nadia , Bright Kelly R. , Slack Donald C. , Uhlmann Donald R. , Gerba Charles P.
Published: January 2008

Biofilms can have deleterious effects on drinking water quality and may harbor pathogens. Experiments were conducted using 100 μg/liter silver to prevent biofilm formation in modified Robbins devices with polyvinyl chloride and stainless steel surfaces. No significant difference was observed on either surface between the silver treatment and the control.
Genetic Dissection of Tropodithietic Acid Biosynthesis by Marine Roseobacters
Authors: Geng Haifeng , Bruhn Jesper Bartholin , Nielsen Kristian F. , Gram Lone , Belas Robert
Published: January 2008

The symbiotic association between the roseobacter
Silicibacter
sp. strain TM1040 and the dinoflagellate
Pfiesteria piscicida
involves bacterial chemotaxis to dinoflagellate-produced dimethylsulfoniopropionate (DMSP), DMSP demethylation, and ultimately a biofilm on the surface of the host. Biofilm formation is coincident with the production of an antibiotic and a yellow-brown pigment. In this report, we demonstrate that the antibiotic is a sulfur-containing compound, tropodithietic acid (TDA). Using random transposon insertion mutagenesis, 12 genes were identified as critical for TDA biosynthesis by the bacteria, and mutation in any one of these results in a loss of antibiotic activity (Tda
−
) and pigment production. Unexpectedly, six of the genes, referred to as
tdaA-F
, could not be found on the annotated TM1040 genome and were instead located on a previously unidentified plasmid (ca. 130 kb; pSTM3) that exhibited a low frequency of spontaneous loss. Homologs of
tdaA
and
tdaB
from
Silicibacter
sp. strain TM1040 were identified by mutagenesis in another TDA-producing roseobacter,
Phaeobacter
sp. strain 27-4, which also possesses two large plasmids (ca. 60 and ca. 70 kb, respectively), and
tda
genes were found by DNA-DNA hybridization in 88% of a diverse collection of nine roseobacters with known antibiotic activity. These data suggest that roseobacters may use a common pathway for TDA biosynthesis that involves plasmid-encoded proteins. Using metagenomic library databases and a bioinformatics approach, differences in the biogeographical distribution between the critical TDA synthesis genes were observed. The implications of these results to roseobacter survival and the interaction between TM1040 and its dinoflagellate host are discussed.
Genome-Scale Metabolic Network Analysis of the Opportunistic Pathogen
Pseudomonas aeruginosa
PAO1
Authors: Oberhardt Matthew A. , Puchałka Jacek , Fryer Kimberly E. , Martins dos Santos Vítor A. P. , Papin Jason A.
Published: January 2008

Pseudomonas aeruginosa
is a major life-threatening opportunistic pathogen that commonly infects immunocompromised patients. This bacterium owes its success as a pathogen largely to its metabolic versatility and flexibility. A thorough understanding of
P. aeruginosa
's metabolism is thus pivotal for the design of effective intervention strategies. Here we aim to provide, through systems analysis, a basis for the characterization of the genome-scale properties of this pathogen's versatile metabolic network. To this end, we reconstructed a genome-scale metabolic network of
Pseudomonas aeruginosa
PAO1. This reconstruction accounts for 1,056 genes (19% of the genome), 1,030 proteins, and 883 reactions. Flux balance analysis was used to identify key features of
P. aeruginosa
metabolism, such as growth yield, under defined conditions and with defined knowledge gaps within the network. BIOLOG substrate oxidation data were used in model expansion, and a genome-scale transposon knockout set was compared against in silico knockout predictions to validate the model. Ultimately, this genome-scale model provides a basic modeling framework with which to explore the metabolism of
P. aeruginosa
in the context of its environmental and genetic constraints, thereby contributing to a more thorough understanding of the genotype-phenotype relationships in this resourceful and dangerous pathogen.
The Genome Sequence of the Tomato-Pathogenic ActinomyceteClavibacter michiganensissubsp.michiganensisNCPPB382 Reveals a Large Island Involved in Pathogenicity
Authors: Gartemann Karl-Heinz , Abt Birte , Bekel Thomas , Burger Annette , Engemann Jutta , Flügel Monika , Gaigalat Lars , Goesmann Alexander , Gräfen Ines , Kalinowski Jörn , Kaup Olaf , Kirchner Oliver , Krause Lutz , Linke Burkhard , McHardy Alice , Meyer Folker , Pohle Sandra , Rückert Christian , Schneiker Susanne , Zellermann Eva-Maria , Pühler Alfred , Eichenlaub Rudolf , Kaiser Olaf , Bartels Daniela
Published: January 2008

Clavibacter michiganensissubsp.michiganensisis a plant-pathogenic actinomycete that causes bacterial wilt and canker of tomato. The nucleotide sequence of the genome of strain NCPPB382 was determined. The chromosome is circular, consists of 3.298 Mb, and has a high G+C content (72.6%). Annotation revealed 3,080 putative protein-encoding sequences; only 26 pseudogenes were detected. Tworrnoperons, 45 tRNAs, and three small stable RNA genes were found. The two circular plasmids, pCM1 (27.4 kbp) and pCM2 (70.0 kbp), which carry pathogenicity genes and thus are essential for virulence, have lower G+C contents (66.5 and 67.6%, respectively). In contrast to the genome of the closely related organismClavibacter michiganensissubsp.sepedonicus, the genome ofC. michiganensissubsp.michiganensislacks complete insertion elements and transposons. The 129-kbchp/tomAregion with a low G+C content near the chromosomal origin of replication was shown to be necessary for pathogenicity. This region contains numerous genes encoding proteins involved in uptake and metabolism of sugars and several serine proteases. There is evidence that single genes located in this region, especially genes encoding serine proteases, are required for efficient colonization of the host. AlthoughC. michiganensissubsp.michiganensisgrows mainly in the xylem of tomato plants, no evidence for pronounced genome reduction was found.C. michiganensissubsp.michiganensisseems to have as many transporters and regulators as typical soil-inhabiting bacteria. However, the apparent lack of a sulfate reduction pathway, which makesC. michiganensissubsp.michiganensisdependent on reduced sulfur compounds for growth, is probably the reason for the poor survival ofC. michiganensissubsp.michiganensisin soil.
Role of Periplasmic Trehalase in Uptake of Trehalose by the Thermophilic Bacterium
Rhodothermus marinus
Authors: Jorge Carla D. , Fonseca Luís L. , Boos Winfried , Santos Helena
Published: January 2008

Trehalose uptake at 65°C in
Rhodothermus marinus
was characterized. The profile of trehalose uptake as a function of concentration showed two distinct types of saturation kinetics, and the analysis of the data was complicated by the activity of a periplasmic trehalase. The kinetic parameters of this enzyme determined in whole cells were as follows:

K
m

= 156 ± 11 μM and
V
max
= 21.2 ± 0.4 nmol/min/mg of total protein. Therefore, trehalose could be acted upon by this periplasmic activity, yielding glucose that subsequently entered the cell via the glucose uptake system, which was also characterized. To distinguish the several contributions in this intricate system, a mathematical model was developed that took into account the experimental kinetic parameters for trehalase, trehalose transport, glucose transport, competition data with trehalose, glucose, and palatinose, and measurements of glucose diffusion out of the periplasm. It was concluded that
R. marinus
has distinct transport systems for trehalose and glucose; moreover, the experimental data fit perfectly with a model considering a high-affinity, low-capacity transport system for trehalose (

K
m

= 0.11 ± 0.03 μM and
V
max
= 0.39 ± 0.02 nmol/min/mg of protein) and a glucose transporter with moderate affinity and capacity (

K
m

= 46 ± 3 μM and
V
max
= 48 ± 1 nmol/min/mg of protein). The contribution of the trehalose transporter is important only in trehalose-poor environments (trehalose concentrations up to 6 μM); at higher concentrations trehalose is assimilated primarily via trehalase and the glucose transport system. Trehalose uptake was constitutive, but the activity decreased 60% in response to osmotic stress. The nature of the trehalose transporter and the physiological relevance of these findings are discussed.
Molecular Characterization of the
Salmonella enterica
Serovar Typhi Vi-Typing Bacteriophage E1
Authors: Pickard Derek , Thomson Nicholas R. , Baker Stephen , Wain John , Pardo Mercedes , Goulding David , Hamlin Nancy , Choudhary Jyoti , Threfall John , Dougan Gordon
Published: January 2008

Some bacteriophages target potentially pathogenic bacteria by exploiting surface-associated virulence factors as receptors. For example, phage have been identified that exhibit specificity for Vi capsule producing
Salmonella enterica
serovar Typhi. Here we have characterized the Vi-associated E1-typing bacteriophage using a number of molecular approaches. The absolute requirement for Vi capsule expression for infectivity was demonstrated using different Vi-negative
S. enterica
derivatives. The phage particles were shown to have an icosahedral head and a long noncontractile tail structure. The genome is 45,362 bp in length with defined capsid and tail regions that exhibit significant homology to the
S. enterica
transducing phage ES18. Mass spectrometry was used to confirm the presence of a number of hypothetical proteins in the Vi phage E1 particle and demonstrate that a number of phage proteins are modified posttranslationally. The genome of the Vi phage E1 is significantly related to other bacteriophages belonging to the same serovar Typhi phage-typing set, and we demonstrate a role for phage DNA modification in determining host specificity.