A novel sulfur-oxidizing autotrophic bacterium, strain J1AT was isolated from a hot spring microbial mat. The cells were Gram-stain-negative, catalase-negative and oxidase-positive. As sole electron donor for chemolithoautotrophic growth, strain J1AT utilized sulfide, thiosulfate, elemental sulfur, and tetrathionate. The G+C content of the genomic DNA was 66 mol%. Major cellular fatty acids (>40 % of total) were C16 : 0 and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c). The predominant quinone was Q-8. Phylogenetic analysis of the 16S rRNA gene indicated that strain J1AT is a relative of species of the genus Thiobacillus, but shares only 93 % or lower sequence similarities with them. On the basis of its properties, strain J1AT represents a novel species of a new genus, for which the name Sulfuritortus calidifontis gen. nov., sp. nov. is proposed. The type strain of the type species is J1AT (=DSM 103923T=NBRC 112474T).