Rhizoferrin: A complexone type siderophore of the mocorales and entomophthorales (Zygomycetes)

The present investigation presents evidence that rhizoferrin, a novel polycarboxylate or complexone-type siderophore, originally isolated from Rhizopus microsporus, represents the common siderophore within the Zygomycetes. Thus, rhizoferrin could be detected by HPLC analysis in various families of the Mucorales, e.g., Rhizopus microsporus var. rhizopodiformis, Mucor mucedo and Phycomyces nitens (Mucoraceae), Chaetostylum fresenii and Cokeromyces recurvatus (Thamnidiaceae), Cunninghamella elegans and Mycotypha africana (Choanephoraceae) and Mortierella vinacea (Mortierellaceae) and in Basidiobolus microsporus (Entomophthorales). The function of rhizoferrin as a siderophore in the fungus R. microsporus var. rhizopodiformis was demonstrated by time- and concentration-dependent uptake of 55Fe]-labelled rhizoferrin, yielding saturation kinetics with values of Km = 8 microM and V(max) = 1.2 nmol min-1 (mg dry wt)-1.