F. L. Thompson, D. Gevers, C. C. Thompson, P. Dawyndt, S. M. Naser, B. Hoste, & J. Swings

We analysed the usefulness of rpoA, recA, and pyrH gene sequences for the identification of vibrios. We sequenced a fragment of these loci of a collection of 208 representative strains, including 192 well-documented Vibrionaceae strains and 16 presumptive Vibrio isolates associated with coral bleaching. In order to determine the intraspecies variation of the three loci, we included several representative strains per species. The phylogenetic trees constructed with the different genetic loci were roughly in agreement with former polyphasic taxonomic studies, including the 16S rRNA-based phylogeny of vibrios. The families Vibrionaceae, Photobacteriaceae, Enterovibrionaceae, and Salinivibrionaceae were all differentiated on the basis of each genetic loci. Each species clearly formed separated clusters with at least 98, 94, 94 % rpoA, recA and pyrH gene sequence similarity. The genus Vibrio was heterogeneous and polyphyletic, with V. fischeri, V. logei and V. wodanis grouping closer to Photobacterium. V. halioticoli-, V. harveyi-, V. splendidus-, and V. tubiashii-related species formed groups within the genus Vibrio. Overall, the three genetic loci were more discriminatory among species than the 16S rRNA. In some cases e.g. within V. splendidus and V. tubiashii group rpoA gene sequences were slightly less discriminatory than recA and pyrH. In these cases, the combination of several loci will yield the most robust identification. We can conclude that strains of the same species will have at least 98, 94, and 94 % rpoA, recA and pyrH gene sequence similarity, respectively.