PT  - JOURNAL ARTICLE
AU  - B. Jesse Shapiro
AU  - Inès Levade
AU  - Gabriela Kovacikova
AU  - Ronald K. Taylor
AU  - Salvador Almagro-Moreno
TI  - Origins of pandemic clones from environmental gene pools
AID  - 10.1101/063115
DP  - 2016 Jan 01
TA  - bioRxiv
PG  - 063115
4099  - http://biorxiv.org/content/early/2016/07/10/063115.short
4100  - http://biorxiv.org/content/early/2016/07/10/063115.full
AB  - Some microbes can transition from an environmental lifestyle to a pathogenic one1–3. This ecological switch typically occurs through the acquisition of horizontally acquired virulence genes4–7. However, the genomic features that must be present in a population prior to 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 one of them reduced the ability of clinical strains to colonize a mammalian host, whereas two other alleles conferred efficient colonization. These results show that VAPs are present in environmental bacterial populations prior to the emergence of virulent clones. We propose a scenario in which VAPs circulate in the environment, they become selected and enriched under certain ecological conditions, and finally a genomic background containing several VAPs acquires virulence factors that allows for its emergence as a pathogenic clone.