Microbial Metabolism of Inorganic Sulfur Compounds

Inorganic sulfur compounds are used by microorganisms (bacteria, fungi, algae) and plants for assimilation, i.e. biosynthesis of sulfur-containing cell constituents. Quantitatively, within the biogeochemical cycle of sulfur the utilization of inorganic sulfur compounds in bacterial energy metabolism, i.e. dissimilatory sulfur utilization, is of far higher importance. Reduced sulfur compounds serve as electron donors for photosynthesis and respiration, whereas inorganic sulfur compounds of oxidation levels above sulfide serve as electron donors in anaerobic respiration as well as in fermentation. In still other bacteria reduced sulfur compounds act as protective agents against hydrogen peroxide.