A novel sulfate-reducing bacterium, strain S28bF(T), was isolated from tidal flat sediment from Tokyo Bay, Japan. Cells of strain S28bF(T) were rod-shaped (0.5-0.6×1.7-3.8 µm), motile and Gram-stain-negative. For growth, the optimum pH was pH 6.8-7.3 and the optimum temperature was 34-42 °C. Strain S28bF(T) used sulfate and thiosulfate as electron acceptors, but not nitrate. The G+C content of the genomic DNA was 56.6 mol%. The fatty acid profile of strain S28bF(T) was characterized by the presence of anteiso-C(15 : 0) and C(16 : 0) as the major components. Phylogenetic analyses based on genes for 16S rRNA, the alpha subunit of dissimilatory sulfite reductase (dsrA) and adenosine-5'-phosphosulfate reductase (aprA) revealed that the isolated strain belonged to the class Deltaproteobacteria. Its closest relative was Desulfosarcina cetonica DSM 7267(T) with a 16S rRNA gene sequence similarity of 93.3 %. Two other strains, S28OL1 and S28OL2 were also isolated from the same sediment. These strains were closely related to S28bF(T) with 16S rRNA gene sequence similarities of 99 %, and the same physiological characteristics were shared with strain S28bF(T). On the basis of phylogenetic and phenotypic characterization, a novel species in a new genus, Desulfatitalea tepidiphila gen. nov., sp. nov., is proposed to accommodate the strains obtained in this study. The type strain is S28bF(T) ( = NBRC 107166(T) = DSM 23472(T)).