Sulfurospirillum diekertiae sp. nov., a tetrachloroethene-respiring bacterium isolated from contaminated soil

Two anaerobic, tetrachloroethene- (PCE-) respiring bacterial isolates, designated strain ACS DCE T and strain ACS TCE , were characterized using a polyphasic approach. Cells were Gram-stain-negative, motile, non-spore-forming and shared a vibrioid- to spirillum-shaped morphology. Optimum growth occurred at 30 °C and 0.1–0.4 % salinity. The pH range for growth was pH 5.5–7.5, with an optimum at pH 7.2. Hydrogen, formate, pyruvate and lactate as electron donors supported respiratory reductive dechlorination of PCE to cis -1,2-dichloroethene ( c DCE) in strain ACS DCE T and of PCE to trichloroethene (TCE) in strain ACS TCE . Both strains were able to grow with pyruvate under microaerobic conditions. Nitrate, elemental sulphur, and thiosulphate were alternative electron acceptors. Autotrophic growth was not observed and acetate served as carbon source for both strains. The major cellular fatty acids were C 16 : 1 ω 7 c , C 16 : 0 , C 14 : 0 and C 18 : 1 ω 7 c . Both genomes feature a circular plasmid. Strains ACS DCE T and ACS TCE were previously assigned to the candidate species 'Sulfurospirillum acididehalogenans'. Here, based on key genomic features and pairwise comparisons of whole-genome sequences, including average nucleotide identity, digital DNA–DNA hybridization and average amino acid identity, strains ACS DCE T and ACS TCE , ' Ca . Sulfurospirillum diekertiae' strains SL2-1 and SL2-2, and the unclassified Sulfurospirillum sp. strain SPD-1 are grouped into one distinct species separate from previously described Sulfurospirillum species. Compared to Sulfurospirillum multivorans and Sulfurospirillum halorespirans , which dechlorinate PCE to c DCE without substantial TCE accumulation, these five strains produce TCE or c DCE as the end product. In addition, some cellular fatty acids (e.g., C 16 : 0 3OH, C 17 : 0 iso 3OH, C 17 : 0 2OH) were detected in strains ACS DCE T and ACS TCE but not in other Sulfurospirillum species. On the basis of phylogenetic, physiological and phenotypic characteristics, 'Ca . Sulfurospirillum acididehalogenans' and 'Ca . Sulfurospirillum diekertiae' are proposed to be merged into one novel species within the genus Sulfurospirillum , for which the name Sulfurospirillum diekertiae sp. nov. is proposed. The type strain is ACS DCE T (=JCM 33349 T = KCTC 15819 T =CGMCC 1.5292 T ).