sulfatereducing

Sulfate reduction, or sulfate-reducing metabolism, is a form of anaerobic respiration in which sulfate (SO4 2−) serves as the terminal electron acceptor. It is carried out by sulfate-reducing microorganisms (SRMs), a diverse group of bacteria and archaea. In this process, organic compounds or molecular hydrogen donate electrons, and sulfate is reduced to hydrogen sulfide (H2S).

The metabolic pathway, known as dissimilatory sulfate reduction, typically proceeds from sulfate to adenosine-5'-phosphosulfate (APS) and then to sulfite before being reduced to sulfide. Enzymes such as sulfate adenylyltransferase (Sat), APS reductase (aprAB), and dissimilatory sulfite reductase (Dsr) drive the reactions. SRMs often occupy energy-limited ecological niches where oxygen is absent, and the energy yield from sulfate reduction is comparatively low.

Ecological and environmental context is broad. SRMs are key players in the sulfur cycle and are commonly found in anoxic sediments, wetlands, freshwater and marine sediments, muds, and anaerobic zones of soils. They also occur in engineered environments such as oil reservoirs, wastewater treatment systems, and anaerobic digesters. Their activity influences organic matter degradation and the cycling of sulfur-containing compounds.

Industrial and health implications are significant. Hydrogen sulfide produced by SRMs can corrode steel and cause souring of oil and gas systems, as well as toxic conditions for other organisms. In anaerobic digestion, SRMs can compete with methanogens, potentially affecting biogas production. Management strategies include sulfate removal, nitrate addition to inhibit SRMs, and biocide treatments.

Diversity among SRMs is high; well-known bacterial genera include Desulfovibrio, Desulfotomaculum, Desulfobacter, and Desulfococcus, with additional archaeal representatives described in certain environments.