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 8.15T [=CECT 7224T, =LMG 23850T], 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 8.15T 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 8.15T (=CECT 7224T, =LMG 23850T).