Iron Uptake Systems in Fungi

Abstract

The highly selective barrier action of cellular membranes applies to all hydrophilic molecules, to which almost all essential ions belong. The strength of this barrier is underscored by its very high resistance and capacitance. However, the barrier action applies much less to hydrophobic, lipophilic molecules. As a consequence, living organisms have developed special mechanisms in order to translocate ions across the lipid bilayer. The majority of fungi synthesize and excrete iron chelating agents to facilitate the permeation of ferric ions across the cytoplasmic membrane. The ferric specific chelating agents of microbial origin are now collectively called siderophores, although there is only limited analogy to the classical ionophores, such as valinomycin, enniatins, nigericins etc.