Arcobacter bivalviorum sp. nov. and Arcobacter venerupis sp. nov., new species isolated from shellfish

A group of ten Arcobacter isolates (Gram negative, slightly curved motile rods, oxidase positive) was recovered from mussels (nine) and from clams (one). These isolates could not be assigned to any known species using the molecular identification methods specific for this genus (16S rDNA-RFLP and m-PCR). The aim of this study is to establish the taxonomic position of these isolates. The 16S rRNA gene sequence similarity of mussel strain F4T to the type strains of all other Arcobacter species ranged from 91.1% to 94.8%. The species most similar to the clams’ strain F67-11T were Arcobacter defluvii (CECT 7697T, 97.1%) and Arcobacter ellisii (CECT 7837T, 97.0%). On the basis of phylogenetic analyses with 16S rRNA, rpoB, gyrB and hsp60 genes, the mussel and clam strains formed two different, new lineages within the genus Arcobacter. These data, together with their different phenotypic characteristics and MALDI-TOF mass spectra, revealed that these strains represent two new species, for which the names Arcobacter bivalviorum (type strain F4T = CECT 7835T = LMG 26154T) and Arcobacter venerupis (type strain F67-11T = CECT 7836T = LMG 26156T) are proposed.