Sulfur metabolism and sulfur cycle

The sulfur cycle was the first biogeochemical cycle to be discovered. In the 1880s, while studying Begiotoa (a bacterium that lives in sulfur-rich environments), Sergei Vinogradsky discovered that this bacterium oxidizes hydrogen sulfide (H2S) as an energy source and replenishes intracellular sulfur droplets. Vingradsky named this form of oxidation metabolism of mineral compounds (inorgoxidation) and worked on it with Salman Waxman until the 1950s.

Sulfur oxidizers can be used as an energy source. These include hydrogen sulfide, pure sulfur, sulfite, thiosulfate, and several polythionates (such as tetrathionate). [29] They rely on enzymes such as sulfur deoxygenase and sulfite oxidase to oxidize sulfur to sulfate. Some bacteria and archaea use hydrogen sulfide in water as an electron donor to perform chemical synthesis. A process similar to photosynthesis and the result will be sugar and they use oxygen as an acceptor atom. Photosynthesizing green sulfur bacteria and purple sulfur bacteria use pure oxygen to carry out such oxidation to make sulfur from hydrogen sulfide. Primitive bacteria that live in the deep oceans next to hydrothermal vents oxidize hydrogen sulfide. The giant ringworm is an example of a large organism that uses hydrogen sulfide as food.

Sulfate-reducing bacteria “breathe” sulfate instead of oxygen. They use inorganic compounds or molecular hydrogen as an energy source and use sulfur as an electron acceptor and reduce sulfur oxides to sulfide (typically hydrogen sulfide). They can grow on other oxidized sulfur groups such as thiosulfate, thionate, polysulfides, and sulfites. The hydrogen sulfide produced by these bacteria causes flatulence.

Sulfur absorbed by plants that absorb it in the form of sulfate through the roots from the soil. Sulfate is reduced to sulfide and then incorporated into cysteine and other organic sulfur compounds.

SO42– → SO32– → H2S → Cysteine → Methionine