Microbial iron transport.

Iron, an essential nutrient, is not readily available in aquatic or terrestrial environments or in animal hosts. Therefore, microbes have developed various strategies for acquiring iron while at the same time protecting themselves from iron's potential toxic effects. The major strategies used by bacteria and fungi to acquire iron include production and utilization of siderophores (ferric specific chelators); utilization of host iron compounds such as heme, transferrin, and lactoferrin; and reduction of Fe(III) to Fe(II) with subsequent transport of Fe(II). Selected examples are discussed with attention to which strategies work best in which environments. The similarities and differences among the different systems with respect to iron binding compounds, receptors, and regulation are also presented.