Desulfurobacterium thermolithotrophum gen. nov., sp. nov., a novel autotrophic, sulphur-reducing bacterium isolated from a deep-sea hydrothermal vent

Researchers isolated a novel thermophilic bacterium, strain BSAT, from a deep-sea hydrothermal chimney at the mid-Atlantic ridge. The organism is a Gram-negative, strictly anaerobic autotroph that grows optimally at 70°C and uses elemental sulfur, thiosulfate, and polysulfides as electron acceptors, reducing them to hydrogen sulfide. The bacterium grows between 40-75°C and pH 4.4-8, with optimal salinity around 35 g/L. Morphologically, cells are small rods (1-2 µm long) with polar flagella and an oblique S-layer lattice covering the cell envelope. Genomic DNA has a 35 mol% GC content. Phylogenetic analysis of 16S rRNA gene sequences shows the organism forms a distinct branch almost equidistant from the orders Aquificales and Thermotogales, indicating it represents a novel genus. Based on its unique phenotypic and phylogenetic characteristics, the authors propose a new genus Desulfurobacterium with the type species D. thermolithotrophum (type strain BSAT, DSM 11699T). The organism displays typical Gram-negative cell envelope architecture and lacks catalase activity.

Key findings

• BSAT is a strictly anaerobic, chemolithoautotrophic thermophile isolated from deep-sea hydrothermal vents that uses hydrogen gas as electron donor and sulfur compounds as electron acceptors
• The organism grows optimally at 70°C, pH 6.0, and 35 g/L sea salt concentration, with doubling time of approximately 135 minutes under optimal conditions
• Phylogenetic analysis of 16S rRNA sequences reveals BSAT forms a distinct phylogenetic position equidistant from orders Aquificales and Thermotogales, warranting classification in a new genus
• BSAT possesses an oblique S-layer lattice with distinctive lattice parameters (11.3 × 6.3 nm) and typical Gram-negative cell envelope with cytoplasmic and outer membranes
• The organism is designated Desulfurobacterium thermolithotrophum gen. nov., sp. nov., representing the first strictly autotrophic, sulfur-reducing bacterium with these characteristics isolated from deep-sea hydrothermal vents