Genomic analysis of Desulfobulbaceae strain B35, a new hydrothermal vent species of mesophilic bacterium that disproportionates sulfur and respires Fe(III).

Desulfobulbaceae sp. nov. strain B35 is a novel mesophilic, anaerobic, chemolithoautotrophic bacterium isolated from the Lucky Strike deep-sea hydrothermal vent on the Mid-Atlantic Ridge, growing autotrophically by disproportionation of elemental sulfur (S0) and thiosulfate (S₂O₃2-), as well as by respiration of Fe(III) using H₂ as an electron donor. Its genome, assembled into 6 contigs totaling 4,140,770 base pairs, has a G + C content of 60.95% and a completeness of 99.4%. It encodes complete metabolic pathways, including the Wood-Ljungdahl pathway for CO₂ fixation, the tricarboxylic acid cycle, and gluconeogenesis. Key sulfur metabolism enzymes (e.g., Sat, AprAB, DsrABCD, DsrMKJOP, QmoABC, thiosulfate reductase-like, various molybdopterin oxidoreductases) and cytochromes involved in Fe(III) reduction are also present. A complete nitrogen fixation pathway for diazotrophic growth is predicted. Additionally, the genome includes numerous defense systems against viral attacks and plasmid invasions, as well as oxidative stress response mechanisms. These traits, including a rich defensome and the genetic capacity to disproportionate various inorganic sulfur compounds and respire diverse electron acceptors, likely enable it to control the flow of genetic information spread by mobile genetic elements via horizontal gene transfer, while adapting to the dynamic conditions of hydrothermal ecosystems, marked by variable availability of reduced compounds.