Sulfur is a key constituent of certain amino acids, proteins, and other biochemicals of both eukaryotes and prokaryotes. For example, sulfur is a component of an enzyme called coenzyme A, which is vital for respiration of plant and animal cells.

Plants are not able to directly use elemental sulfur. Instead, they rely on the ability of certain types of bacteria to convert elemental sulfur to another form. Bacteria that are known as chemoautotrophic bacteria can combine sulfur with water and oxygen to produce hydrogen sulfate. Plants are able to incorporate the sulfate compound into proteins.

Bacteria can participate in the reduction of sulfur, in which the sulfur compounds act as an electron receptor, or in the oxidation of sulfur, in which an electron is removed from the sulfur compound.

Hydrogen sulfide, a gas that has the characteristic smell of rotten eggs, is...