ContrastingInter-andIntraspeciesRecombinationPatternsin the “Harveyi Clade” Vibrio Collected over Large Spatial and Temporal Scales

urbanczyk, henryk ; ogura, yoshitoshi ; hayashi, tetsuya;

Recombination plays an important role in the divergence of bacteria, but the frequency of inter species and intraspecies recombination events remains poorly understood. We investigated recombination events that occurred within core genomes of 35 Vibrio strains (family Vibrionaceae, Gammaproteobacteria), from six closely related species in the so-called “Harveyi clade.” The strains were selected from acollection of strains isolated in the last 90 years, from various environments world wide. We found a close relationship between the number of inter species recombination events within coregenomes of the 35 strains and the over all genomic identity,as inferred from calculations of the average nucleotide identity. The relationship between the over all nucleotide identity and the number of detected interspecies recombination events was comparable when analyzing strains isolated over 80 years apart, from different hemispheres, or from different ecologies, as well as in strains isolated from the same geographic location within a short time frame. We further applied the same method of detecting recombination events to analyze 11 strains of Vibrio campbellii, and identified disproportionally high number of intraspecies recombination events within the coregenomes of some, butnotall, strains. The high number of recombination events was detected between V. campbellii strains that have significant temporal (over 18 years) and geographical (over10,000km) differences in their origins of isolation. Results of this study reveala remarkable stability of Harvey iclade species, and give clues about the origins and persistence of species in the clade