Description of Two New Thermophilic Desulfotomaculum spp., Desulfotomaculum putei sp. nov., from a Deep Terrestrial Subsurface, and Desulfotomaculum luciae sp. nov., from a Hot Spring

Six strains of thermophilic, endospore-forming, sulfate-reducing bacteria were enriched and isolated from 2.7 km below the earth’s surface in the Taylorsville Triassic Basin in Virginia. The cells of these strains were motile rods that were 1 to 1.1 µm in diameter and 2 to 5 µm long. The cells grew by oxidizing H2, formate, methanol (weakly), lactate (incompletely, to acetate and CO2), or pyruvate (incompletely) while reducing sulfate to sulfide; acetate did not serve as a catabolic substrate. Thiosulfate or sulfite could replace sulfate as an electron acceptor. The results of a phylogenetic analysis of the 16S rRNA gene indicated that these strains belong to the genus Desulfotomaculum, but are distinct from previously described Desulfotomaculum species. Thus, we propose a new species, Desulfotomaculum putei, for them, with strain TH-11 (= SMCC W459) as the type strain. The results of our phylogenetic analysis also indicated that strain SLTT, which was isolated from a hot spring and has been described previously (T. M. Karnauchow, S. F. Koval, and K. F. Jarrell, Syst. Appl. Microbiol. 15:296–310, 1992), is also a member of the genus Desulfotomaculum and is distinct from other species in this genus. We therefore propose the new species Desulfotomaculum luciae for this organism; strain SLT (= SMCC W644) is the type strain of D. luciae.