How does the global sulfur cycle connect organic sulfur compounds with sulfide and sulfate ions?

The global sulfur cycle facilitates the continuous movement of sulfur between organic and inorganic forms through biological and geochemical processes.12

From Organic Sulfur to Inorganic Ions

Organic sulfur compounds, such as those found in proteins and amino acids, enter the cycle when organisms die and decompose. Soil microorganisms degrade these proteins into constituent amino acids, which are subsequently converted into hydrogen sulfide (H₂S). In the presence of oxygen, sulfur bacteria further oxidize this hydrogen sulfide into elemental sulfur and eventually into sulfate ions (SO₄²⁻).123

From Inorganic Ions to Organic Sulfur

Plants and microorganisms take up sulfate ions from the environment and convert them into organic forms, incorporating them into their biological structures. Animals then acquire these organic sulfur compounds by consuming these plants or other organisms.2

This cycle is further influenced by anaerobic respiration, where sulfate-reducing bacteria convert sulfate back into hydrogen sulfide, particularly in waterlogged soils, sewage, and marine sediments.23