A novel sulfate-reducing bacterium,strain S606T,was isolated from a sulfide sample collected at a depth of 2764 m from a deep-sea chimney wall in the Indian Ocean.Phylogenetic 16S rRNA gene sequence analyses placed strain S606T within the genus Thermodesulfatator,with highest sequence similarity of 98.15% to Thermodesulfatator indicus DSM 15286T,followed by Thermodesulfatator atlanticus ATl325T (97.4%).The average nucleotide identity (ANI) values between strain S606T and two type strains (T.indicus DSM 15286T and T.atlanticus AT1325T) were 79.2% and 71.5%,respectively.The digital DNA-DNA hybridization estimate values between strain S606T and two type strains were 22.7+2.4% and 18.1+2.3%,respectively.Cells were Gram-negative,anaerobic,motile rods (1-1.8 × 0.5-0.7 μm).The novel isolate grew at NaCl concentrations ranging from 1.5 to 4.5% (optimum 2.5-3%),from pH 5.5 to 8 (optimum 6.5-7) and at temperatures between 50 and 80 ° (optimum 65-70 ℃).Strain S606T grew chemolithoautotrophically in an H2/CO2 atmosphere (80/20,v/v;200 kPa),used sulfate as a terminal electron acceptor,but not sulfur,sulfite nor thiosulfate.The predominant fatty acids were C16∶0 (24.17%),summed feature 8 (C18∶1 ω6c and/or C18∶1 ω7c,26.33%),C18∶0 (22%) and C18∶ ω9c (9.17%).The DNA G+C content of the chromosomal DNA was 43.1 mol% as determined using the whole genome sequence.The combined genotypic and phenotypic traits show that strain S606T should be described as a novel species of the genus Thermodesulfatator,for which the name Thermodesulfatator autotrophicus sp.nov.is proposed,with the type strain S606T (=DSM 101864T=MCCC 1A01871T).