Final answer:
Oxidation of sulfur in the sulfur cycle primarily turns hydrogen sulfide into elemental sulfur and then sulfate. These sulfates are then assimilated by plants or transformed back into hydrogen sulfide by sulfate-reducing bacteria and archaea. Human activities exacerbate this cycle through emissions resulting in acid rain.
Step-by-step explanation:
In the sulfur cycle, the oxidation of sulfur, primarily by microbes such as anoxygenic photosynthetic bacteria and chemoautotrophic archaea and bacteria, leads to its transformation from hydrogen sulfide (H2S) into elemental sulfur (S°), and eventually into sulfate (SO4²-).
This sulfate is then available in the environment for plants to absorb and integrate into amino acids like cysteine and methionine, which are crucial for protein formation. Conversely, sulfate-reducing bacteria and archaea can use sulfate as a final electron acceptor in anaerobic respiration, which converts it back to hydrogen sulfide.
Human activities, particularly the burning of fossil fuels, release substantial amounts of sulfur dioxide (SO2) into the atmosphere, contributing to acid rain and environmental damage.