Chemical characterization of fungal siderophores.

Siderophores of twenty fungi belonging to Zygomycotina (5 Mucorales), Ascomycotina (7 aspergilli, 6 penicillia, Neurospora crassa) and Deuteromycotina (Fusarium dimerum) were examined for their chemical nature. Siderophores produced by fungi other than Mucorales were all hydroxamates. Mucorales produced carboxylate siderophores. Catecholate type of siderophores were not detectable. Hydroxamate siderophores were mostly (9 out of 15) trihydroxamates, while six were dihydroxamates. Monohydroxamate nature was not shown by any of the 15 test fungal siderophores. In ligand properties, 12 out of 15 hydroxamate siderophores formed hexadentate ligands, while two formed tetradentates and one bidentate. There was good correlation between number of hydroxamate groups and ligand property.