Phylogeny of Vibrio cholerae based on recA sequence

Abstract

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

FIG. 1

Partial sequence for the recA gene of the El Tor strain N16961, as aligned with 111 other analyzed sequences. An asterisk below the base indicates that the base is conserved in all 112 strains; a period indicates that the base varies in at least one strain. The hyphen at bp 201 is to accommodate strain C0545, which has a 1-bp insertion at this point and a 1-bp deletion 11 bp later.

FIG. 2

Neighbor-joining tree of selected strains of Vibrio. The numbers on the branches indicate the number of the nucleotide changes; terminal branch lengths were suppressed.