The transition metal elements V, Mo, W, Mn, Fe, Co, Ni, Cu, and Zn serve as osmotic regulators, as structural glue, and as catalytic centers for hundreds of cellular reactions. The significance of metals in biological catalysis is underscored by the fact that greater than one-third of all characterized enzymes are metalloenzymes. Thus metals serve important functions in all facets of bacterial metabolism.

Bacterial metalloenzymes exert a major catalytic force on the biosphere by mediating a large number of important reactions in elemental cycles where biological systems play important roles. Because microorganisms are the key players in recycling carbon, hydrogen, nitrogen, oxygen, and sulfur on the Earth's surface, bacterial enzymes that contain iron, molybdenum, manganese, nickel, and copper are, by transference, the agents responsible for the cycling of these elements.