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

Abstract

A novel mesophilic, obligately anaerobic, facultatively sulphur-reducing bacterium, designated strain IC12T, 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 IC12T were 15-40 °C (optimum, 30-35 °C), 10-60 g l-1 (optimum, 20-30 g l-1) 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 IC12T were C14 : 0, C16 : 0 and C16 : 1 ω7. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that strain IC12T was affiliated to the phylum Fusobacteriota and was most closely related to Ilyobacter insuetus VenChi2T (86.5 % sequence similarity). Strain IC12T 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 in silico DNA-DNA hybridization between strain IC12T and related strains of the phylum Fusobacteriota were 71.4 and 26.4 %, respectively. Phylogenomic, physiological and chemotaxonomic analyses indicate that strain IC12T represents a novel genus and species within the phylum Fusobacteriota, for which the name Haliovirga abyssi gen. nov., sp. nov. is proposed, with strain IC12T (= DSM 112164T=JCM 39166T) as the type strain. We also propose the family Haliovirgaceae fam. nov. to accommodate this novel genus.