ABSTRACT
This chapter presents recent progress on the molecular biology of siderophore biosynthesis and its regulation in Ustilago maydis. The major role of siderophores is to bind iron(III) very strongly and participate in the transport of iron into the microbial cells under conditions of cellular iron deprivation. Hydroxamate siderophores produced by most fungal genera can be divided into three families: the ferrichromes; the coprogens; and the fusarinines. The development of molecular genetic tools has provided the groundwork for rapid progress in our understanding of iron transport in microorganisms, especially in prokaryotic systems. Iron uptake systems of microorganisms are regulated by iron-dependent mechanisms. In bacteria, regulation of a wide variety of genes including at least five separate iron transport systems and a series of other iron-regulated genes are governed by the Fur gene that encodes an iron-dependent repressor. A siderophore-mediated high affinity iron uptake system consists of siderophores and their cognate membrane-bound transport system.
