title: Diversity of Clinical and Environmental Isolates of Vibrio cholerae in Natural Transformation and Contact-Dependent Bacterial Killing Indicative of Type VI Secretion System Activity.
abstract: The bacterial pathogen Vibrio cholerae can occupy both the human gut and aquatic reservoirs, where it may colonize chitinous surfaces that induce the expression of factors for three phenotypes: chitin utilization, DNA uptake by natural transformation, and contact-dependent bacterial killing via a type VI secretion system (T6SS). In this study, we surveyed a diverse set of 53 isolates from different geographic locales collected over the past century from human clinical and environmental specimens for each phenotype outlined above. The set included pandemic isolates of serogroup O1, as well as several serogroup O139 and non-O1/non-O139 strains. We found that while chitin utilization was common, only 22.6% of the isolates tested were proficient at chitin-induced natural transformation, suggesting that transformation is expendable. Constitutive contact-dependent killing of Escherichia coli prey, which is indicative of a functional T6SS, was rare among clinical isolates (only 4 of 29) but common among environmental isolates (22 of 24). These results bolster the pathoadaptive model in which tight regulation of T6SS-mediated bacterial killing is beneficial in a human host, whereas constitutive killing by environmental isolates may give a competitive advantage in natural settings. Future sequence analysis of this set of diverse isolates may identify previously unknown regulators and structural components for both natural transformation and T6SS.
authors.affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, USA.
authors.forename: Eryn E
authors.initials: EE
authors.lastname: Bernardy
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Maryann A
authors.initials: MA
authors.lastname: Turnsek
authors.affiliation: University of Wisconsin-Madison, Madison, Wisconsin, USA.
authors.forename: Sarah K
authors.initials: SK
authors.lastname: Wilson
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Cheryl L
authors.initials: CL
authors.lastname: Tarr
authors.affiliation: School of Biology, Georgia Institute of Technology, Atlanta, Georgia, USA brian.hammer@biology.gatech.edu.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Hammer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D044822:Biodiversity; D002686:Chitin / Q000378:metabolism; D002688:Chitinases / Q000235:genetics / Q000378:metabolism; D002771:Cholera / Q000382:microbiology*; D004269:DNA, Bacterial / Q000378:metabolism; D004783:Environmental Microbiology; D006801:Humans; D010641:Phenotype; D014169:Transformation, Bacterial; D000069376:Type VI Secretion Systems / Q000235:genetics / Q000502:physiology*; D014734:Vibrio cholerae / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D000069376:Type VI Secretion Systems; D002686:Chitin; D002688:Chitinases