Pyrobaculum oguniense sp nov., a novel facultatively aerobic and hyperthermophilic archaeon growing at up to 97 °C

A novel hyperthermophilic, heterotrophic, rod-shaped archaeon was isolated from a terrestrial hot spring at Oguni-cho, Kumamoto Prefecture, Japan. The new isolate, strain TE7(T), grew under aerobic, microaerobic and anaerobic conditions. Isolate TE7(T) grew optimally at 90-94 degreesC and ph 7.0-7.5 (adjusted at 25 degreesC) under atmospheric air with vigorous shaking. Strain TE7(T) cells were motile rods 2-10 mum in length and covered with a surface-layer lattice. Cell yields at 90 degreesC under aerobic conditions were twice that under anaerobic conditions. Under aerobic conditions, growth was inhibited by elemental sulfur, but thiosulfate stimulated growth. Under anaerobic conditions, no growth was observed in the presence of nitrate and nitrite, but elemental sulfur, thiosulfate, L-cystine and oxidized glutathione stimulated growth. The 165 rDNA sequence of TE7(T) exhibited a close relationship to the sequences of Pyrobaculum aerophilum and Thermoproteus neutrophilus, which belong to the cluster of the genus Pyrobaculum. DNA-DNA hybridization analysis showed a low level of DNA similarity between TE7(T) and previously described Pyrobaculum species. As TE7(T) is phenotypically and phylogenetically different from the other members of this genus, it is described as a new species named Pyrobaculum oguniense (type strain TE7(T) = JCM 10595(T) = DSM 13380(T)).