Phylogeny of Vibrio cholerae based on recA sequence

We sequenced a 705-bp fragment of the recA gene from 113 Vibrio cholerae st rains and closely related species. One hundred eighty-seven nucleotides wer e phylogenetically informative, 55 were phylogenetically uninformative, and 463 were invariant. Not unexpectedly, Vibrio parahaemolyticus and Vibrio v ulnificus strains formed out-groups; we also identified isolates which rese mbled V. cholerae biochemically but which did not cluster with V. cholerae. In many instances, V. cholerae serogroup designations did not correlate wi th phylogeny, as reflected by recA sequence divergence. This observation is consistent with the idea that there is horizontal transfer of O-antigen bi osynthesis genes among V. cholerae strains.