Quorum Sensing Contributes to Natural Transformation of Vibrio cholerae in a Species-Specific Manner

Melanie Blokesch, Patrick Martin Seitz, Gaia Francesca Marianne Suckow
American Society for Microbiology, 2011
Article

Although it is a human pathogen, Vibrio cholerae is a regular member of aquatic habitats, such as coastal regions and estuaries. Within these environments, V. cholerae often takes advantage of the abundance of zooplankton and their chitinous molts as a nutritious surface on which the bacteria can form biofilms. Chitin also induces the developmental program of natural competence for transformation in several species of the genus Vibrio. In this study, we show that V. cholerae does not distinguish between species-specific and non-species-specific DNA at the level of DNA uptake. This is in contrast to what has been shown for other Gram-negative bacteria, such as Neisseria gonorrhoeae and Haemophilus influenzae. However, species specificity with respect to natural transformation still occurs in V. cholerae. This is based on a positive correlation between quorum sensing and natural transformation. Using mutant-strain analysis, cross-feeding experiments, and synthetic cholera autoinducer-1 (CAI-1), we provide strong evidence that the species-specific signaling molecule CAI-1 plays a major role in natural competence for transformation. We suggest that CAI-1 can be considered a competence pheromone.

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Melanie Blokesch, Patrick Martin Seitz, Gaia Francesca Marianne Suckow
American Society for Microbiology, 2011
Article

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https://infoscience.epfl.ch/record/168288?ln=fr

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Bactérie

Le terme bactérie est un nom vernaculaire qui désigne certains organismes vivants microscopiques et procaryotes présents dans tous les milieux. Le plus souvent unicellulaires, elles sont parfois plu

Compétence (biologie)

En biologie, la compétence est la capacité d'une cellule à prélever une molécule d'ADN libre dans son environnement par le phénomène de transformation. On distingue la compétence naturelle de certain

Vibrio cholerae

Vibrio cholerae (le vibrion cholérique ou le bacille virgule en français) est une bactérie à gram négatif, en forme de bâtonnet incurvé, mobile et responsable chez l'Homme du choléra, une maladi

Horizontal gene transfer (HGT) is widespread in bacteria and archaea and plays a significant role in prokaryotic evolution. One mode of HGT is natural competence for genetic transformation, which allows the organism to take up free DNA from its surroundings and incorporate this DNA into its own genome. Natural transformation has been studied in many diverse organisms since its discovery in the 1920s; however, the majority of these studies were primarily based on population-wide methods. Recent advances in biological imaging, including the use of fluorescent proteins, have revolutionized the field of microbiology, and such imaging techniques allow for the study of important phenomena at the single-cell level. Here, we describe the visualization of the DNA uptake process in naturally competent Vibrio cholerae cells. More precisely, the protocol below provides instructions for the genetic engineering of V. cholerae to generate strains carrying translational fusion constructs between important competence/recombination and fluorescent proteins. Moreover, detailed steps for live cell time-lapse microscopy imaging of these strains under competence-inducing conditions are discussed for direct or indirect visualization of the DNA uptake process.

Humana Press2015

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Chitin colonization, chitin degradation and chitin-induced natural competence of Vibrio cholerae are subject to catabolite repression

Melanie Blokesch

Although Vibrio cholerae is a human pathogen its primary habitat are aquatic environments. In this environment, V. cholerae takes advantage of the abundance of zooplankton, whose chitinous exoskeletons provide a nutritious surface. Chitin also induces the developmental programme of natural competence in several species of the genus Vibrio. Because the chitin surface can serve as the sole carbon source for V. cholerae, the link between carbon catabolite repression and chitin-induced natural competence for transformation was investigated in this study. Provision of competing phosphoenolpyruvate: carbohydrate phosphotransferase system (PTS)-dependent carbon sources in addition to chitin significantly lowered natural transformability. These sugars are known to interfere with the accumulation of 3,5- cyclic AMP (cAMP); therefore, the contributions of the cAMP-producing enzyme, adenylate cyclase and the cAMP receptor protein (CRP) to chitin surface colonization, chitin degradation and natural transformation were also analysed. The results provided here indicate that cAMP and CRP are important in at least three interlinked areas of the chitin-induced natural competence programme. First, cAMP and CRP are required for the efficient colonization of the chitin surface; second both contribute to chitin degradation and utilization, and third, cAMP plus CRP play a role in increasing competence gene expression. These findings highlight the complex regulatory circuit of chitininduced natural competence in V. cholerae.

Wiley-Blackwell2012

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ComEA Is Essential for the Transfer of External DNA into the Periplasm in Naturally Transformable Vibrio cholerae Cells

Melanie Blokesch, Roman Bulushev, Matteo Dal Peraro, Hasan Pezeshgi Modarres, Aleksandra Radenovic, Patrick Martin Seitz, Lorenz Jan Steinbock

The DNA uptake of naturally competent bacteria has been attributed to the action of DNA uptake machineries resembling type IV pilus complexes. However, the protein(s) for pulling the DNA across the outer membrane of Gram-negative bacteria remain speculative. Here we show that the competence protein ComEA binds incoming DNA in the periplasm of naturally competent Vibrio cholerae cells thereby promoting DNA uptake, possibly through ratcheting and entropic forces associated with ComEA binding. Using comparative modeling and molecular simulations, we projected the 3D structure and DNAbinding site of ComEA. These in silico predictions, combined with in vivo and in vitro validations of wild-type and sitedirected modified variants of ComEA, suggested that ComEA is not solely a DNA receptor protein but plays a direct role in the DNA uptake process. Furthermore, we uncovered that ComEA homologs of other bacteria (both Gram-positive and Gram-negative) efficiently compensated for the absence of ComEA in V. cholerae, suggesting that the contribution of ComEA in the DNA uptake process might be conserved among naturally competent bacteria.

Public Library Science2014

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