Parasulfuritortus cantonensis gen. nov., sp. nov., a microaerophilic sulfur-oxidizing bacterium isolated from freshwater sediment

A novel sulfur-oxidizing bacterium, designated strain LSR1(T), was enriched and isolated from a freshwater sediment sample collected from the Pearl River in Guangzhou, PR China. The strain was an obligate chemolithoautotroph, using thiosulfate or sulfide as an electron donor and energy source. Growth of strain LSR1(T) was observed at 15-40 degrees C, pH 6.0-7.5 and NaCl concentrations of 0-1.5 %. Strain LSR1(T) was microaerophilic, with growth only at oxygen content less than 10%. Anaerobic growth was also observed when using nitrate as the sole electron acceptor. The major cellular fatty acids were C-16:0 and summed feature 3 (comprising C-16:1 omega 7c and/or C-16:1 omega 6c). The DNA G+C content of the draft genome sequence was 67.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain LSR1(T) formed a lineage within the family Thiobacillaceae, showing sequence identities of 92.87, 92.33 and 90.80% with its closest relative genera Sulfuritortus, Annwoodia and Thiobacillus, respectively. The genome of strain LSR1(T) contained multiple genes encoding sulfur-oxidizing enzymes that catalyse thiosulfate and sulfide oxidation, and the gene encoding cbb(3)-type cytochrome c oxidase and bd-type quinol oxidase, which enables strain LSR1(T) to perform sulphur oxidation under microaerophilic conditions. On the basis of phenotypic, genotypic and phylogenetic results, strain LSR1(T) is considered to represent a novel species of a new genus Parasulfuritortus within the family Thiobacillaceae, for which the name Parasulfuritortus cantonensis gen. nov., sp. nov. is proposed. The type strain is LSR1(T) (=GDMCC 1.1549=JCM 33645).