The Fate of Intracellular Metal Ions in Microbes

Metals are essential for all microorganisms as they are required as cofactors of enzymes that mediate metabolic processes that are indispensable for cellular energy production and growth. Some metals, such as zinc, are readily bound and serve as key structural elements of many macromolecules. Thus, to grow, microorganisms have an essential quota for several metals. The catalytic and other chemical properties of metals that microorganisms value create issues for metal management. Due to their high affinity for amino acids and their reactive nature, uptake, intracellular transport, and storage of metals are mediated by tightly regulated proteins. Protein chaperones function to supply some specific metals to sites of utilization and, in some cases, storage. In particular, iron is difficult to acquire and is stored as a mineral in protein nanocages. Other metals, when present in excess, induce the expression of export systems to maintain a defined intracellular concentration of readily exchangeable metal.