Reduction of Elemental Sulfur by Moderately Thermophilic Organotrophic Bacteria and the Description of Thermoanaerobacter sulfurophilus sp. nov.

A high number of anaerobic organotrophic thermophilic bacteria able to reduce elemental sulfur to hydrogen sulfide was found in a thermophilic cyanobacterial mat in the Uzon caldera (Kamchatka). Two spore- forming and one non-spore-forming strains were isolated and shown to be fermentative organisms. The presence of elemental sulfur was not essential but had a strong stimulating effect on growth. The non-spore-forming strain L-64 is a gram-negative rod-shaped bacterium with peritrichous flagellation able to ferment a wide range of car- bohydrates and reduce elemental sulfur and thiosulfate to hydrogen sulfide. Based on phenotypic properties, the results of 16S rDNA sequencing, and the DNA-DNA homology, strain L-64 (DSM 11584) was affiliated to the genus Thermoanaerobacter as a representative of a new species, Thermoanaerobacter sulfurophilus sp. nov.