ABSTRACT
This chapter concentrates on siderophores produced by fungi. It covers the uptake processes of ferrisiderophores in fungi that have been studied. Natural hydroxamate siderophores are sometimes tetradentate but mostly hexadentate, that is, the molecule contains either two or three hydroxamate groups. The albomycins, potent antibiotics against both gram-positive and gram-negative bacteria, belong to the ferrichrome family. They are hydroxamates derived from a linear ornithine peptide structure. Siderophores have both hydrophilic and lipophilic characterisics, which is the basis for the extraction procedures used originally for isolation. This isolation method, however, has been replaced by XAD chromatography. The crucial event leading to the rapid entrance of iron into the fungal cells is the interaction of siderophores with the membrane located siderophore transport systems. Time-dependent measurements are required to determine the actual transport rates, while concentration-dependent measurements are designed to determine whether or not saturation of a transport system or diffusion is involved.
