Vibrio celticus sp. nov., a new Vibrio species belonging to the Splendidus clade with pathogenic potential for clams

A group of four motile facultative anaerobic marine isolates (Rd 8.15 T [=CECT 7224 T, =LMG 23850 T], Rd 16.13, Rd 6.8 [=LMG 25696] and Rd2L5) were obtained from cultured clams ( Ruditapes philippinarum and Venerupis pullastra) in Galicia, north-western Spain. They formed a tight phylogenetic group based on sequences of the 16S rRNA gene and the four housekeeping genes rpoA (encoding the α-chain of RNA polymerase), rpoD (encoding the sigma factor of RNA polymerase), recA (encoding RecA protein), and atpA (encoding the α-subunit of bacterial ATP synthase). The phylogenies based on these sequences indicated that the four isolates represented a novel species in the genus Vibrio, and more precisely in the Splendidus clade. DNA–DNA hybridizations with the type strains of species showing more than 98.6% 16S rRNA gene sequence similarity, revealed a DNA–DNA relatedness below 70%. The isolates could be differentiated from the phylogenetically related Vibrio species on the basis of several phenotypic features. In addition, strain Rd 8.15 T showed potential pathogenic activity for adult clams in virulence assays. The name Vibrio celticus sp. nov. is proposed for this new taxon, with the type strain being Rd 8.15 T (=CECT 7224 T, =LMG 23850 T).