Hydrogenivirga okinawensis sp nov., a thermophilic sulfur-oxidizing chemolithoautotroph isolated from a deep-sea hydrothermal field, Southern Okinawa Trough

A novel extremely thermophilic sulfur-oxidizing bacterium, strain LS12-2(T), was isolated from a deep-sea hydrothermal field at the Yonaguni Knoll IV, Southern Okinawa Trough. Cells of strain LS12-2(T) were motile rods, 1.5-4.0 mu m in length and 0.4-0.5 mu m in width. Strain LS12-2(T) was an obligate chemolithoautotroph that could utilize elemental sulfur or thiosulfate as an electron donor and nitrate or oxygen as an electron acceptor. Growth was observed at 65-85 degrees C (optimum 70-75 degrees C), pH 5.8-8.3 (optimum pH 6.9-7.5), 1.0-4.0% (w/v) NaCl (optimum 2.5%) and 1.0-7.0% O-2 in the gas phase (optimum 3.0%). Fatty acids detected were C-16:0 (8.0%), C-18:0 (9.0%), C-18:1 (62.5%) and C-20:1 (20.5%). The genomic DNA G+C content was 51.3 mol%. 16S rRNA gene sequence analysis indicated that strain LS12-2(T) belonged to the genus Hydrogenivirga. Based on physiological and phylogenetic characteristics of the isolate, it is proposed that this strain represents a novel species in the genus Hydrogenivirga, Hydrogenivirga okinawensis sp. nov. The type strain of Hydrogenivirga okinavvensis is LS12-2(T) (=JCM 13302(T) =DSM 17378(T)).