Deferribacter desulfuricans sp. nov., a novel sulfur-, nitrate- and arsenate-reducing thermophile isolated from a deep-sea hydrothermal vent

Researchers isolated and characterized a novel thermophilic bacterium, Deferribacter desulfuricans, from a deep-sea hydrothermal vent chimney at Suiyo Seamount, Japan. The organism is a strictly anaerobic, heterotrophic thermophile that grows optimally between 60-65°C and pH 6.5. It uses various organic compounds (yeast extract, amino acids, ethanol, organic acids) as energy and carbon sources, with hydrogen serving as a supplementary energy source. Uniquely, it requires elemental sulfur, nitrate, or arsenate as electron acceptors, reducing them to sulfide, nitrite, or arsenite respectively. The bacterium exhibits bent, flexible rod morphology with a polar flagellum and is extremely oxygen-sensitive. Phylogenetic analysis shows 98.1% 16S rDNA sequence similarity to D. thermophilus, but DNA-DNA hybridization (5.8%) and physiological differences distinguish it as a separate species. Key distinctions include its ability to use elemental sulfur as a primary electron acceptor and its inability to reduce iron(III) or manganese(IV), unlike D. thermophilus. The discovery expands knowledge of thermophilic bacteria in deep-sea hydrothermal environments.

Key findings

• D. desulfuricans is a novel anaerobic thermophile requiring sulfur, nitrate, or arsenate as electron acceptors, distinguishing it from the related D. thermophilus which uses iron(III) and manganese(IV)
• The organism grows optimally at 60-65°C and pH 6.5, is strictly anaerobic with extreme oxygen sensitivity, and uses organic compounds and hydrogen for metabolism
• Despite 98.1% 16S rDNA sequence similarity to D. thermophilus, DNA-DNA hybridization shows only 5.8% relatedness, confirming species-level separation
• The isolate was recovered from a deep-sea hydrothermal vent chimney at Suiyo Seamount, indicating these environments harbor diverse sulfur-reducing thermophiles beyond commonly isolated Thermococcales and Thermotogales