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Sulfur-reducing Bacteria

Sulfur-reducing bacteria are microorganisms that are able to use respiratory sulfur reduction to conserve energy. They can reduce and other oxidized forms of sulfur to  but are unable to reduce. There are more than 25 genera of dissimilative sulfur-reducers spread across five bacterial and archaeal phyla. Most sulfur-reducing bacteria are Proteobacteria, primarily Deltaproteobacteria (e.g., Desulfuromonas, Pelobacter, Desulfurella, Geobacter), with some genera residing in the Epsilon-(e.g., Wolinella and Sulfurospirillum) and Gammaproteobacteria(e.g., Shewanella and Pseudomonas mendocina). Other sulfur-reducing bacteria are species of Firmicutes (e.g., Desulfitobacterium and Ammonifex), Aquificae (e.g., Desulfurobacterium and Aquifex), Synergistetes (e.g., Dethiosulfovibrio), or Deferribacteres(e.g., Geovibrio).

Physiology of sulfur-reducing Bacteria

The physiology of sulfur reducers is more diverse than that of sulfate reducers. Most sulfur reducers are obligate anaerobes, but facultatively aerobic species are common, they are often able to reduce electron acceptors such as nitrate, ferrous iron, or thiosulfate as alternatives to.

Their physiology is characterized by whether they completely oxidize acetate and other fatty acids to. Species of Desulfuromonas are complete oxidizers that grow anaerobically by coupling the oxidation of acetate, succinate, ethanol, or propanol to the reduction of. In contrast, Sulfospirillum and Wolinella are incomplete oxidizers and cannot use acetate as an electron donor. Sulfospirillum can reduce using either or formate as electron donor.

Sulfur-reducing bacteria reside in many of the same habitats as sulfate-reducing bacteria and often form associations with bacteria that oxidize to, such as green sulfur bacteria.

The produced from  oxidation is then reduced back to  during metabolism of the sulfur reducer,completing an anoxic sulfur cycle. 