Molecular Genetics of Iron Uptake and Homeostasis in Fungi

Abstract

Most prokaryotes and all eukaryotes require iron for their growth. This transition metal has two readily available ionization states, ferrous and ferric iron, and thus is involved in a great variety of enzymatic processes including electron transfer in respiration, redox reactions carried out by numerous oxygenases and hydrogenases, and DNA-synthesis. While iron is one of the most abundant metals on earth, in aerobic environments it is present mostly in very insoluble compounds such as oxyhydroxide polymers. Consequently, the concentration of ferric iron in solution at neutral pH is probably not greater than 10-18M (Neilands 1995). On the other hand, an excess of iron within cells can be deleterious, because of the potential to catalyze the generation of cell damaging reactive oxygen species. Therefore, microbes have developed various highly regulated systems for iron uptake and storage.