Pyrofollis japonicus gen. nov. sp. nov., a novel member of the family Pyrodictiaceae isolated from the Iheya North hydrothermal field.

A novel hyperthermophilic, heterotrophic archaeon, strain YC29, was isolated from a deep-sea hydrothermal vent in the Mid-Okinawa Trough, Japan. Cells of strain YC29 were non-motile, irregular cocci with diameters of 1.2-3.0 µm. The strain was an obligatory fermentative anaerobe capable of growth on complex proteinaceous substrates. Growth was observed between 85 and 100 °C (optimum 90-95 °C), pH 4.9-6.4 (optimum 5.1), and in the presence of 1.4-4.0% (w/v) NaCl (optimum 3.0%). Inorganic carbon was required as a carbon source. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that the isolate was a member of the family Pyrodictiaceae. The genome size was 2.02 Mbp with a G+C content of 49.4%. The maximum values for average nucleotide identity (ANI), average amino acid identity (AAI), and in silico DNA-DNA hybridization (dDDH) value of strain YC29 with relatives were 67.9% (with Pyrodictium abyssi strain AV2), 61.1% (with Pyrodictium occultum strain PL-19), and 33.8% (with Pyrolobus fumarii strain 1A), respectively. Based on the phylogenetic, genomic, and phenotypic characteristics, we propose that strain YC29 represents a novel genus and species, Pyrofollis japonicus gen. nov., sp. (type strain YC29 = DSM 113394 = JCM 39171).