[ODP-073] Genomic dissection of the Vibrio cholerae O-serogroup global reference strains
Vibrio cholerae is a member of the Vibrionaceae family that is found in coastal waters and estuaries, and more than 200 serogroups have been identified. However, only two O-serogroups, O1 and O139, are associated with severe, life-threatening diarrheal disease cholera and responsible for its global pandemics. The epidemiological or genomic studies on O1 and O139 have been reported frequently, but the genetic diversity of V. cholerae population have yet to be elucidated and their understandings are limited. In this study, we determined the genome sequences of 206 O-serogroup reference strains and performed phylogenetic and pan-genome analysis for V. cholerae population. Pan-genome analysis demonstrated that the V. cholerae pan-genome could be considered “open” with size increasing logarithmically. This result indicated the V. cholerae population increased the genetic diversity to acquire exogenous genes from the natural habitats. In addition, V. cholerae population can be phylogenetically separated into mainly 3 clusters with statistical significance. However, number of core genes identified in chromosome 1 and 2 was exactly same regardless of cluster, indicating no exchange event for any core genes between two chromosomes. Our results could be an important clue to give us a deep understanding of V. cholerae evolutionary processes.