ISOLATION AND IDENTIFICATION OF HYDROXAMATE SIDEROPHORES OF ERICOID MYCORRHIZAL FUNGI

Three ericoid mycorrhizal fungi were grown in pure culture under iron deprivation: (i) the ascomycete Hymenoscyphus ericae, a characteristic endophyte of ericaceous plants on acid soils; (ii) the hyphomycete Oidiodendron griseum, an ericoid mycorrhizal fungus which is also a soil-borne fungus able to colonize wood; and (iii) an endophyte of the calciculous ericaceous plant Rhodothamnus chamaecistus. All three fungi produced several hydroxamate siderophores which were isolated in the ferric form by adsorption to Amberlite XAD-2, gel chromatography on Sephadex LH20 and by HPLC on a C18 reversed-phase column. Siderophores were identified by (i) co-chromatography with known fungal siderophores, (ii) ion spray mass spectrometry after semi-preparative HPLC and (iii) analyzing their electrophoretic behavior. While H. ericae and O. griseum were similar in producing ferricrocin as their principal siderophore, the endophyte of R. chamaecistus produced mainly fusigen.