Sulfurovum lithotrophicum gen. nov., sp. nov., a novel sulfur-oxidizing chemolithoautotroph within the {varepsilon}-Proteobacteria isolated from Okinawa Trough hydrothermal sediments

A novel mesophilic sulfur- and thiosulfate-oxidizing bacterium, strain 42BKT^T, was isolated from the gas-bubbling sediment at the Iheya North hydrothermal system in the mid-Okinawa Trough, Japan. The isolate was a Gram-negative, non-motile and coccoid to oval-shaped bacterium. Growth was observed at 1040 °C (optimum 2830 °C) and in the pH range 5·09·0 (optimum 6·57·0). Strain 42BKT^T grew chemolithoautotrophically with elemental sulfur or thiosulfate as a sole electron donor and oxygen (optimum 5 % in gas phase) or nitrate as an electron acceptor. The G+C content of the genomic DNA was 48·0 mol%. Phylogenetic analysis based on the 16S rRNA gene sequence indicated that the isolate belonged to the previously uncultivated Group F within the -Proteobacteria, which includes phylotypes of vent epibiont and environmental sequences from global deep-sea cold seep and hydrothermal vent fields. On the basis of the physiological and molecular characteristics of this isolate, the type species of a novel genus, Sulfurovum lithotrophicum gen. nov., sp. nov., is proposed. The type strain is 42BKT^T (=ATCC BAA-797^T=JCM 12117^T).