Moorella Sulfitireducens Sp. Nov., a Thermophilic Anaerobic Bacterium Isolated from a Terrestrial Thermal Spring

In hydrothermal ecosystems, the dissolution of sulfur dioxide in water results in the formation of sulfite, which can be used in microbial metabolism. A limited number of thermophiles have been isolated using sulfite as an electron acceptor. From a terrestrial thermal spring, Sakhalin Island, Russia, we isolated a thermophilic anaerobic bacterium (strain SLA38). Cells of strain SLA38 were spore-forming straight rods. Growth was observed at temperatures 45-65 °C (optimum at 60 °C) and pH 5.5-9.0 (optimum at pH 6.5-7.0). The novel isolate was capable of anaerobic respiration with sulfite, thiosulfate, fumarate and perchlorate or fermentative growth. Strain SLA38 utilized glycerol, lactate, pyruvate and yeast extract. It grew lithoautotrophically on carbon monoxide with thiosulfate as electron acceptor, producing acetate. The genome size of the isolate was 2.9 Mbp and genomic DNA G + C content was 53.6 mol%. Analysis of the 16S rRNA gene sequences revealed that strain SLA38 belongs to the genus Moorella. Based on the physiological features and phylogenetic analysis, we propose to assign strain SLA38 to a new species of the genus Moorella, as Moorella sulfitireducens sp. nov. The type strain is SLA38 (= DSM 111068 = VKM B-3584).