title: Origins of pandemic Vibrio cholerae from environmental gene pools.
abstract: Some microorganisms can transition from an environmental lifestyle to a pathogenic one1-3. This ecological switch typically occurs through the acquisition of horizontally acquired virulence genes4,5. However, the genomic features that must be present in a population before the acquisition of virulence genes and emergence of pathogenic clones remain unknown. We hypothesized that virulence adaptive polymorphisms (VAPs) circulate in environmental populations and are required for this transition. We developed a comparative genomic framework for identifying VAPs, using Vibrio cholerae as a model. We then characterized several environmental VAP alleles to show that while some of them reduced the ability of clinical strains to colonize a mammalian host, other alleles conferred efficient host colonization. These results show that VAPs are present in environmental bacterial populations before the emergence of virulent clones. We propose a scenario in which VAPs circulate in the environment and become selected and enriched under certain ecological conditions, and finally a genomic background containing several VAPs acquires virulence factors that allow for its emergence as a pathogenic clone.
authors.affiliation: Department of Biological Sciences, University of Montreal, Montreal, Quebec H2V 2S9, Canada.
authors.forename: B Jesse
authors.initials: BJ
authors.lastname: Shapiro
authors.affiliation: Department of Biological Sciences, University of Montreal, Montreal, Quebec H2V 2S9, Canada.
authors.forename: Inès
authors.initials: I
authors.lastname: Levade
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Kovacikova
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA.
authors.forename: Ronald K
authors.initials: RK
authors.lastname: Taylor
authors.affiliation: Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA.|Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida 32827, USA.
authors.forename: Salvador
authors.initials: S
authors.lastname: Almagro-Moreno