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Global sulfur cycle entails the transformations of sulfur species through different oxidation states, which play a vital role in both geological and biological processes. Steps involved in the sulfur cycle include; Mineralization of organic sulfur into inorganic forms, such as hydrogen sulfide (H2S), elemental sulfur, as well as sulfide minerals.
Oxidation of hydrogen sulfide, sulfide, and elemental sulfur (S) to sulfate (SO42−).
Reduction of sulfate to sulfide.
Incorporation of sulfide into organic compounds (including metal-containing derivatives).
The bacteria involved in the sulfur cycle are classified into two general categories, including sulfate reducing bacteria (SRBs) and sulfide-oxidizing bacteria (SOBs). SOBs play an important role in reducing sulfide and SRBs in reducing sulfate and heavy metals from the environment