Aspergillus nidulans and Penicillium chrysogenum produce specific cellular siderophores in addition to the well-known siderophores of the culture medium. Since this was found previously in Neurospora crassa, it is probably generally true for filamentous ascomycetes. The cellular siderophore of A. nidulans is ferricrocin; that of P. chrysogenum is ferrichrome. A. nidulans also contains triacetylfusigen, a siderophore without apparent biological activity. Conidia of both species lose siderophores at high salt concentrations and become siderophore dependent. This has also been found in N. crassa, where lowering of the water activity has been shown to be the causal factor. We used an assay procedure based on this dependency to reexamine the extracellular siderophores of these species. During rapid mycelial growth, both A. nidulans and P. chrysogenum produced two highly active, unidentified siderophores which were later replaced by a less active or inactive product--coprogen in the case of P. chrysogenum and triacetylfusigen in the case of A. nidulans. N. crassa secreted coprogen only. Fungal siderophore metabolism is varied and complex.

The highly active extracellular siderophores previously detected in young cultures of Aspergillus nidulans and Penicillium chrysogenum have been identified as the cyclic ester fusigen (fusarinine C), and its open-chain form, fusigen B (fusarinine B).

Aspergillus nidulans and Penicillium chrysogenum produce specific cellular siderophores in addition to the well-known siderophores of the culture medium. Since this was found previously in Neurospora crassa, it is probably generally true for filamentous ascomycetes. The cellular siderophore of A. nidulans is ferricrocin; that of P. chrysogenum is ferrichrome. A. nidulans also contains triacetylfusigen, a siderophore without apparent biological activity. Conidia of both species lose siderophores at high salt concentrations and become siderophore dependent. This has also been found in N. crassa, where lowering of the water activity has been shown to be the causal factor. We used an assay procedure based on this dependency to reexamine the extracellular siderophores of these species. During rapid mycelial growth, both A. nidulans and P. chrysogenum produced two highly active, unidentified siderophores which were later replaced by a less active or inactive product--coprogen in the case of P. chrysogenum and triacetylfusigen in the case of A. nidulans. N. crassa secreted coprogen only. Fungal siderophore metabolism is varied and complex.