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Linking the natural competence program of Vibrio cholerae to its environmental niche.

English title Linking the natural competence program of Vibrio cholerae to its environmental niche.
Applicant Blokesch Melanie
Number 127029
Funding scheme Project funding (Div. I-III)
Research institution Global Health Institute EPFL SV-DO
Institution of higher education EPF Lausanne - EPFL
Main discipline Experimental Microbiology
Start/End 01.01.2010 - 31.12.2012
Approved amount 288'599.00
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All Disciplines (2)

Discipline
Experimental Microbiology
Molecular Biology

Keywords (8)

Natural competence; Bacterial evolution; Environmental niche; Regulation; Vibrio cholerae; signal transduction; environment; evolution of pathogens

Lay Summary (English)

Lead
Lay summary
There is increasing concern about the emergence of new infectious agents and the threat this poses to global health. Knowledge of how pathogens emerge, why it happens repeatedly and how it can be predicted or controlled is of fundamental importance for human health. Vibrio cholerae serves as an excellent model system to study the evolution of bacterial pathogens as it exhibits two distinct lifestyles. Between infectious cycles it has been frequently associated with the chitin exo-skeleton of zooplankton in marine habitats. As a facultative pathogen, however, it possesses the ability to colonize the human intestine followed by the onset of the disease cholera. While there is a reasonable understanding on this host-microbe interaction, knowledge of the environmental life of V. cholerae is still limiting. It was recently shown that chitin, in addition to serving as a carbon and nitrogen source, acts as an essential inducer of natural competence in V. cholerae. Natural competence is a mode of horizontal gene transfer as it allows the uptake of extracellular DNA from the environment followed by its recombination into the cell's genome. Thus, the genetic repertoire of V. cholerae can be enhanced and diversified leading to novel phenotypes including those that specify new metabolic pathways or novel pathogenic traits. The environmental and molecular cues involved in the onset of the competence program are largely unknown and represent the main focus of this research proposal. Preliminary data showed that initiation of the competence program in V. cholerae is not only dependent on chitin as an inducer, but also requires increasing population density, nutrient limitation and stress. How these environmental and physiological signals are sensed and transduced via a hierarchy of regulators in addition to how this balance is achieved across spatial and temporal dimensions will be investigated. The goals of this project will be achieved through the use of genetic screens, transcription profiling, protein detection methods and visualization of gene expression at the single cell level. This work will help us to understand the link between the ecology of V. cholerae and its ability to evolve towards a human pathogen.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
ComEA Is Essential for the Transfer of External DNA into the Periplasm in Naturally Transformable Vibrio cholerae Cells.
Seitz Patrick, Pezeshgi Modarres Hassan, Borgeaud Sandrine, Bulushev Roman D, Steinbock Lorenz J, Radenovic Aleksandra, Dal Peraro Matteo, Blokesch Melanie (2014), ComEA Is Essential for the Transfer of External DNA into the Periplasm in Naturally Transformable Vibrio cholerae Cells., in PLoS genetics, 10(1), 1004066-1004066.
Composition of the DNA-uptake complex of Vibrio cholerae.
Metzger Lisa C, Blokesch Melanie (2014), Composition of the DNA-uptake complex of Vibrio cholerae., in Mobile genetic elements, 4(1), 28142-28142.
The Lifestyle of Vibrio cholerae Fosters Gene Transfers
Blokesch Melanie (2014), The Lifestyle of Vibrio cholerae Fosters Gene Transfers, in ASM Microbe, 9(2), 64-70.
A quorum sensing-mediated switch contributes to natural transformation of Vibrio cholerae
Blokesch Melanie (2013), A quorum sensing-mediated switch contributes to natural transformation of Vibrio cholerae, in Mobile Genetic Elements, 2(5), 1.
A transcriptional regulator linking quorum sensing and chitin induction to render Vibrio cholerae naturally transformable.
Lo Scrudato Mirella, Blokesch Melanie (2013), A transcriptional regulator linking quorum sensing and chitin induction to render Vibrio cholerae naturally transformable., in Nucleic Acids Research, 41(6), 3644-3658.
Cues and regulatory pathways involved in natural competence and transformation in pathogenic and environmental Gram-negative bacteria.
Seitz Patrick, Blokesch Melanie (2013), Cues and regulatory pathways involved in natural competence and transformation in pathogenic and environmental Gram-negative bacteria., in FEMS microbiology reviews, 37(3), 336-63.
DNA-uptake machinery of naturally competent Vibrio cholerae.
Seitz Patrick, Blokesch Melanie (2013), DNA-uptake machinery of naturally competent Vibrio cholerae., in Proc Natl Acad Sci USA, 110(44), 17987-17992.
Evidence for Two Different Regulatory Mechanisms Linking Replication and Segregation of Vibrio cholerae Chromosome II
Venkova-Canova Tatiana, Baek Jong Hwan, FitzGerald Peter C., Blokesch Melanie, Chattoraj Dhruba K. (2013), Evidence for Two Different Regulatory Mechanisms Linking Replication and Segregation of Vibrio cholerae Chromosome II, in PLoS Genetics, 9(6), e1003579.
Overexpression of the tcp gene cluster using the T7 RNA polymerase/promoter system and natural transformation-mediated genetic engineering of Vibrio cholerae
Borgeaud Sandrine, Blokesch Melanie (2013), Overexpression of the tcp gene cluster using the T7 RNA polymerase/promoter system and natural transformation-mediated genetic engineering of Vibrio cholerae, in PloS one, 8(1), e53952.
Chitin colonization, chitin degradation and chitin-induced natural competence of Vibrio cholerae are subject to catabolite repression.
Blokesch Melanie (2012), Chitin colonization, chitin degradation and chitin-induced natural competence of Vibrio cholerae are subject to catabolite repression., in Environmental microbiology, 14(8), 1898-1912.
The Regulatory Network of Natural Competence and Transformation of Vibrio cholerae
Lo Scrudato Mirella, Blokesch Melanie (2012), The Regulatory Network of Natural Competence and Transformation of Vibrio cholerae, in PLoS Genetics, 8(6), e1002778-17.
TransFLP – a method to genetically modify V. cholerae based on natural transformation and FLP-recombination
Blokesch Melanie (2012), TransFLP – a method to genetically modify V. cholerae based on natural transformation and FLP-recombination, in J. Vis. Exp., 8(68), e3761.
Quorum sensing contributes to natural transformation of Vibrio cholerae in a species-specific manner.
Suckow Gaia, Seitz Patrick, Blokesch Melanie (2011), Quorum sensing contributes to natural transformation of Vibrio cholerae in a species-specific manner., in Journal of bacteriology, 193(18), 4914-24.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ISME 2012 Talk given at a conference 19.08.2012 Copenhagen, Denmark Blokesch Melanie;
2nd Mol Micro Meeting Würzburg Poster 25.04.2012 Wuerzburg, Germany, Germany Blokesch Melanie;
Vibrio 2011 Talk given at a conference 02.11.2011 Santiago de Compostela / Spain, Spain Blokesch Melanie;
FEMS 2011 (4th Congress of the FEMS) Talk given at a conference 26.06.2011 Geneva / Switzerland, Switzerland Blokesch Melanie;
Mol Micro Meeting Würzburg Talk given at a conference 04.05.2011 Würzburg / Germany, Germany Blokesch Melanie;


Associated projects

Number Title Start Funding scheme
143356 Understanding the dynamics of competence induction and DNA uptake in Vibrio cholerae 01.01.2013 Project funding (Div. I-III)

Abstract

There is increasing concern about the emergence of new infectious agents and the threat this poses to human health. As the bacterium Vibrio cholerae exhibits two distinct lifestyles, one associated with the chitin exoskeleton of zooplankton in marine habitats and the other as a cholera-causing colonizer of the human intestine, it will serve as a model system to study the evolution of bacterial pathogens.While there is a reasonable understanding on the host-pathogen interaction, knowledge of the environmental life of V. cholerae is still limited. We recently showed that chitin, in addition to serving as a carbon and nitrogen source, acts as an essential inducer of natural competence in V. cholerae. Natural competence is a mode of horizontal gene transfer as it allows the uptake of extracellular DNA from the environment followed by its recombination into the cell’s genome. Accordingly, natural competence contributes to the enhancement and diversification of the bacterium’s genetic repertoire. However, the environmental and physiological signals involved in the regulation of the competence program are largely unknown and represent the main focus of this proposal. Preliminary data showed that initiation of the competence program in V. cholerae is not only dependent on chitin as an inducer, but also requires increasing population density, nutrient limitation and stress. How these signals are sensed and transduced via a hierarchy of regulators in addition to how this balance is achieved across spatial and temporal dimensions in biofilms formed on chitin surfaces will be studied.To address these questions in detail, I propose two specific aims:Specific Aim 1: Identify the regulatory network of the competence program. Determine the competence regulon including essential transcription factors and genes they regulate. Investigate how regulation of the competence genes is modulated by external signals. Determine how carbon catabolism is involved in competence. Investigate whether V. cholerae actively secretes DNA or undergoes fratricide, and finally determine if the DNA up-take process is specific to certain types of DNA.Specific Aim 2: Map single components of the natural competence / transformation program onto a timeline. Establish single cell expression analysis. Study crucial events and their chronology.These specific aims will be achieved through the use of genetic screens, transcription profiling, protein detection methods and visualization of gene expression at the single cell level using epifluorescence and confocal laser scanning microscopy. The proposed work program will integrate basic microbial genetics with the fields of genomics, bacterial physiology, ecology and evolution and their effects on bacterial pathogenicity. The final goal is to understand the link between the ecology of V. cholerae and its ability to evolve towards a human pathogen.
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