The genome of the Gram-positive metal- and sulfate-reducing bacterium <i> Desulfotomaculum reducens</i> strain MI-1

Spore-forming, Gram-positive sulfate-reducing bacteria (SRB) represent a group of SRB that dominates the deep subsurface as well as niches in which resistance to oxygen and dessication is an advantage. <i>Desulfotomaculum reducens</i>; strain MI-1 is one of the few cultured representatives of that group with a complete genome sequence available. The metabolic versatility of this organism is reflected in the presence of genes encoding for the oxidation of various electron donors, including three- and four-carbon fatty acids and alcohols. Synteny in genes involved in sulfate reduction across all four sequenced Gram-positive SRB suggests a distinct sulfate-reduction mechanism for this group of bacteria. Based on the genomic information obtained for sulfate reduction in <i>D. reducens</i>;, the transfer of electrons to the sulfite and APS reductases is proposed to take place via the quinone pool and heterodisulfide reductases respectively. In addition, both H2-evolving and H2-consuming cytoplasmic hydrogenases were identified in the genome, pointing to potential cytoplasmic H2 cycling in the bacterium. The mechanism of metal reduction remains unknown.