sulfideoxidizing

Sulfideoxidizing, also written sulfide-oxidizing, refers to the chemical and biological processes that convert reduced sulfur species, such as hydrogen sulfide (H2S) or bisulfide (HS−), into more oxidized forms like elemental sulfur (S0), sulfite (SO3^2−), thiosulfate (S2O3^2−), or sulfate (SO4^2−). In biogeochemical cycles, sulfide oxidation releases energy that can be harvested by microorganisms or occur abiotically under appropriate redox conditions.

Abiotic sulfide oxidation occurs when sulfide reacts with oxidants such as molecular oxygen or ferric iron. This can lead to the formation of elemental sulfur or sulfate, depending on the oxidant, pH, and environmental conditions. The rate of chemical oxidation is influenced by factors like oxygen concentration, pH, temperature, and the presence of catalysts such as iron minerals.

Biological sulfide oxidation is carried out by sulfide-oxidizing bacteria and some archaea, collectively known as SOB. These chemolithoautotrophs oxidize reduced sulfur compounds to derive energy, coupling the oxidation to the reduction of electron acceptors such as oxygen or nitrate and fixing carbon dioxide into biomass. Enzymatic pathways commonly involved include the Sox multienzyme system and, in some organisms, the reverse dissimilatory sulfite reductase pathways. SOB are found in diverse environments, including marine and freshwater sediments, hydrothermal vents, cold seeps, and oxic-anoxic interfaces.

Sulfide oxidation plays a central role in the sulfur cycle and affects environmental processes such as metal mobility, acid mine drainage management, and bioremediation. It also has implications for corrosion and the productivity of various ecosystems where reduced sulfur compounds accumulate.