RT Journal Article SR Electronic(1) A1 Nakagawa, Satoshi A1 Takai, Ken A1 Inagaki, Fumio A1 Horikoshi, Koki A1 Sako, YoshihikoYR 2005 T1 Nitratiruptor tergarcus gen. nov., sp. nov. and Nitratifractor salsuginis gen. nov., sp. nov., nitrate-reducing chemolithoautotrophs of the ε-Proteobacteria isolated from a deep-sea hydrothermal system in the Mid-Okinawa Trough JF International Journal of Systematic and Evolutionary Microbiology, VO 55 IS 2 SP 925 OP 933 DO https://doi.org/10.1099/ijs.0.63480-0 PB Microbiology Society, SN 1466-5034, AB Two novel denitrifying bacteria, designated strains MI55-1T and E9I37-1T, were isolated from deep-sea hydrothermal vent chimney structures at the Iheya North hydrothermal field in the Mid-Okinawa Trough, Japan. Both isolates were strict chemolithoautotrophs growing by respiratory nitrate reduction with H2, forming N2 as a metabolic product. Oxygen (at low concentrations) could serve as an alternative electron acceptor for growth of the isolates. Growth of strain MI55-1T was observed at temperatures between 40 and 57 °C (optimum, 55 °C; doubling time, 2 h), at pH values between 5·4 and 6·9 (optimum, pH 6·4) and in the presence of between 1·5 and 4·0 % (w/v) NaCl (optimum, 2·5 %). Growth of strain E9I37-1T was observed at temperatures between 28 and 40 °C (optimum, 37 °C; doubling time, 2·5 h), at pH values between 5·6 and 7·6 (optimum, pH 7·0) and in the presence of between 1·5 and 3·5 % (w/v) NaCl (optimum, 3·0 %). The G+C contents of the genomic DNA of strains MI55-1T and E9I37-1T were 29·6 and 35·5 mol%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains MI55-1T and E9I37-1T belonged to groups A and F of the ε-Proteobacteria, but that they had distant phylogenetic relationships with any species, within the phylogenetic groups, that had validly published names (sequence similarities were less than 91 %). On the basis of the physiological and molecular characteristics of the novel isolates, it is proposed that they should each be classified in a novel genus: Nitratiruptor tergarcus gen. nov., sp. nov., with MI55-1T (=JCM 12459T=DSM 16512T) as the type strain, and Nitratifractor salsuginis gen. nov., sp. nov., with E9I37-1T (=JCM 12458T=DSM 16511T) as the type strain., UL https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.63480-0