Strategy and tactics in the evolution of iron acquisition

To acquire iron, all species have had to overcome the problems of iron insolubility and toxicity. This review surveys the approaches taken in solubilizing and transporting iron by species in different kingdoms. In some instances, iron uptake systems are novel and are restricted to a few species or to a biologic kingdom. In other instances, it is clear that all organisms use homologous genes. With rare exceptions, ferrous iron (Fe(2+)) transport systems are not specific for iron and will effect uptake of other transition metals. Ferric iron (Fe(3+)) transport systems are highly specific for iron, and in vertebrates are used to target iron transport to specific tissues.