MYCORRHIZAL FUNGI - SIDEROPHORE PRODUCTION

Mycorrhizal fungi, which commonly occur in natural as well as agricultural soils, are known to enhance plant uptake of nutrients, including metal ions present as trace concentrations. As mycorrhizal infection is a widespread feature of plant communities, it seems appropriate to review the data on mycorrhizal fungi and their potential to produce siderophores. Based on a bioassay with Aureobacterium flavescens JG-9 it was shown that a number of ectomycorrhizal fungi (EM) produce hydroxamate siderophores. Also an arbuscular mycorrhizal (AM) grass species, which showed greater iron uptake than nonmycorrhizal controls, tested positively when bioassayed for hydroxamate siderophores. Ericoid mycorrhizal fungi, too, have been demonstrated to be capable of producing hydroxamate-type siderophores. However, only in the case of the eridoid mycorrhizal fungi the main siderophons have been isolated and subsequently identified as ferricrocin and fusigen, respectively. The biotechnological and ecological significance of studies of the siderophore biosynthesis by mycorrhizal fungi is discussed.