Hydrogenivirga caldilitoris gen. nov., sp nov., a novel extremely thermophilic, hydrogen- and sulfur-oxidizing bacterium from a coastal hydrothermal field

A novel extremely thermophilic, hydrogen- and sulfur-oxidizing bacterium, designated strain IBSK3(T), was isolated from a coastal hot spring in lbusuki, Kagoshima Prefecture, Japan. The cells were motile, straight to slightly curved rods (1(.)2-3(.)0 mum long and 0-3-0-4 mum wide), Strain IBSK3T was an obligate chemolithoautotroph growing by respiratory nitrate reduction with H-2, forming N2O as an end product. Low concentrations of O-2 (0-4-7-7 %, v/v; optimum 2-0 %, v/v) could serve as an alternative electron acceptor to growth. In addition, strain IBSK3T was able to utilize elemental sulfur as a sole electron donor with either nitrate or low concentrations Of 02 as an electron acceptor. Growth was observed between 55 and 77-5 degreesC (optimum 75 degreesC; 2 h doubling time), pH 5-5 and 8-3 (optimum pH 6-5-7-0)(1) and in the presence of 0(.)5 and 4(.)0% NaCl (optimum 2-0 %). The G +C content of the genomic DNA was 49(.)2 mol%. On the basis of 16S rRNA gene sequence analysis, strain IBSK3T belonged to the family Aquificaceae, but it only demonstrated a distant phylogenetic relationship with any recognized species within the family (sequence similarity was less than 92 %). On the basis of the physiological and molecular characteristics of the novel isolate, a new genus and novel species are proposed: the type strain of Hydrogenivirga caldilitoris gen. nov., sp. nov. is IBSK3(T) (=jCM 12173(T) =ATCC BAA-821(T)).