gen. nov., sp. nov., a mesophilic fermentative bacterium isolated from the Iheya North hydrothermal field, and proposal of fam. nov.

A novel mesophilic, obligately anaerobic, facultatively sulphur-reducing bacterium, designated strain IC12, was isolated from a deep-sea hydrothermal field in the Mid-Okinawa Trough, Japan. The cells were Gram-negative, motile, short rods with a single polar flagellum. The ranges and optima of the growth temperature, NaCl concentration and pH of strain IC12 were 15-40 °C (optimum, 30-35 °C), 10-60 g l (optimum, 20-30 g l) and pH 4.9-6.7 (optimum, pH 5.8), respectively. Yeast extract was utilized as a sole carbon and energy source for fermentative growth. Major fatty acids of strain IC12 were C, C and C ω7. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that strain IC12 was affiliated to the phylum and was most closely related to VenChi2 (86.5 % sequence similarity). Strain IC12 contained a chromosome of 2.43 Mbp and a large plasmid of 0.30 Mbp. The G+C content of the genomic DNA was 26.4 mol%. The maximum values for average nucleotide identity and DNA-DNA hybridization between strain IC12 and related strains of the phylum were 71.4 and 26.4 %, respectively. Phylogenomic, physiological and chemotaxonomic analyses indicate that strain IC12 represents a novel genus and species within the phylum , for which the name gen. nov., sp. nov. is proposed, with strain IC12 (= DSM 112164=JCM 39166) as the type strain. We also propose the family fam. nov. to accommodate this novel genus.