Analysis of RNA Polymerase Beta Subunit (rpoB) Gene Sequences for the Discriminative Power of Marine Vibrio Species

In the present study, we sequenced the RNA polymerase beta subunit (rpoB) gene of marine Vibrio species and assessed its discriminative power in identifying vibrios. Both the rpoB and 16S rRNA sequences of 29 phenotypically different Vibrio strains isolated from coastal waters were determined. Molecular and phylogenetic comparisons of the sequences of these two genes classified the 29 strains into 11 different species. The resolution of the Vibrio spp. on the rpoB phylogenetic tree was approximately three times greater than that on the 16S rRNA phylogenetic tree. Moreover, by comparing the rpoB sequences of 98 marine γ-Proteobacteria, including 38 marine Vibrio species, Vibrio-specific primers were developed to amplify a 730-bp fragment of the rpoB gene. Using these primers, we successfully detected Vibrio signals in environmental samples and determined their relative abundances via comparisons with known standards. This rpoB-targeting polymerase chain reaction assay can be used efficiently to monitor relative Vibrio abundance in marine waters.