AN ANALYSIS OF THE V1 AND V2 REGIONS OF VIBRIO-CHOLERAE AND VIBRIO-MIMICUS 16S RIBOSOMAL-RNA

The V1 and V2 variable regions of the 168 rRNA gene of three strains o f V. cholerae and one strain of V. mimicus were amplified by PCR. Frag ments containing both regions were cloned into M13mp18 using Smal and sequenced by the dideoxy method. The 263-bp sequence from a strain iso lated during the 1991 cholera outbreak in Brazil was deposited in Genb ank under the accession number L05178. Except for an extra G in one of the strains, the three V. cholerae sequences were identical. The V. m imicus sequence was very similar, with only two substitutions. We comp ared these sequences with the Vibrio 16S rRNA sequences described by D orsch at al. in 1992. It was noted that the V1 region, including helix 6 and its associated loop, comprised two different sizes and sequence s in the various Vibrio species. While V. cholerae, V. mimicus, V. vul nificus, V. anguillarum and V. diazotrophicus had a 46-nucleotide V1, other species such as V. parahaemolyticus, V. proteolyticus, V. algino lyticus, V. campbellii and V. hollisae had longer 54- or 55-nucleotide regions, with a different consensus sequence. The phylogeny of Vibrio was analysed using the sequenced region and its equivalent in other s pecies, by means of the ''Phylip'' software package. Species with a sh ort helix 6 were grouped together, as were species with a long helix. Dorsh et al.'s analysis is discussed in relation to this ''helix 6 spl it''.