Multilocus sequence analysis of putative Vibrio mediterranei strains and description of Vibrio thalassae sp. nov.

A multilocus sequence analysis based on partial gyrB, mreB, rpoD and pyrH genes was undertaken with 61 putative Vibrio mediterranei/V. shilonii strains from different hosts (mussels, oysters, clams, coral, fish and plankton) or habitat (seawater and sediment) and geographical origins (Mediterranean, Atlantic and Pacific). A consistent grouping was obtained with individual and concatenated gene sequences, and the clade, comprising 54 strains, was split into three subclades by all methods: subclade A (40 strains, including AK1, the former type strain of Vibrio shilonii), subclade B (8 strains) corresponding to the species V. mediterranei, and subclade C (six strains) representing a new species, V. thalassae sp. nov., with strain MD16(T) (=CECT 8203(T)=KCTC 32373(T)) as the proposed type strain. Average nucleotide identity (ANI) values, determined as a measure of genomic similarity, confirmed these assignments, and supported that strains in subclade C were a different species from V. mediterranei, with ANIb and ANIm figures lower than 90.0%. The synonymy of V. shilonii and V. mediterranei was also stressed by both MLSA and ANI determinations (97.0% between both type strains). No connection was found between geographic origin or sample type and MLSA grouping.