sp. nov., a mesophilic sulphate-reducing bacterium isolated from a xenic culture of an anaerobic heterolobosean protist.

A novel sulphate-reducing bacterium, strain SYK, was isolated from a xenic culture of an anaerobic protist obtained from a sulphidogenic sediment of the saline Lake Hiruga in Fukui, Japan. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that SYK clustered with the members of the genus . The closest relative of strain SYK was SF6, with 16S rRNA gene sequence identity of 97.43 %. Digital DNA-DNA hybridisation and average nucleotide identity values between SYK and species of the genus fell below the respective thresholds for species delineation, indicating that SYK represents a novel species of the genus . Cells measured 1.7-3.7×0.2-0.5 µm in size and were Gram-stain-negative, obligately anaerobic, motile by means of a single polar flagellum and had a curved rod or sigmoid shape. Cell growth was observed under saline conditions from pH 6.0 to 9.5 (optimum pH 8.0-9.0) and at a temperature of 10-30 °C (optimum 25 °C). SYK used lactate, pyruvate, fumarate, formate and H as electron donors. It used sulphate, sulphite, thiosulphate and sulphur as terminal electron acceptors. Pyruvate and fumarate were fermented. Major cellular fatty acids were anteiso-C, C, anteiso-Cω9, summed feature 3 (Cω6 and/or Cω7) and summed feature 8 (Cω7 and/or Cω6). The DNA G+C content of SYK was 49.4 mol%. On the basis of the the genetic and phenotypic features, SYK was determined to represent a novel species of the genus for which the name sp. nov. is proposed with type strain SYK (=DSM 114958=JCM 35746).