CHEMICAL-STRUCTURE AND BIOLOGICAL-ACTIVITY OF A SIDEROPHORE PRODUCED BY RHIZOPUS-ARRHIZUS

Rhizopus arrhizus grown on low-Fe medium produces a siderophore, the c hemical structure of which was determined by means of H-1 nuclear magn etic resonance (NMR), C-13 NMR, and circular dichroism spectroscopy. T he siderophore was identified as (1-oxo-3-hydroxy-3,4-dicarboxybutyl)- diaminobutane chemically identical to rhizoferrin produced by Rhizopus microsporus. Growth promotion of R. arrhizus by several unferrated ch elates in Fe-limited medium was studied in microtitration plates. The impact of rhizoferrin was much more pronounced than the effect of othe r siderophores. This growth promotion was used as a bioassay for the d etection of rhizoferrin. Purified Fe-rhizoferrin was found to be a ver y efficient Fe source for tomato plants [Lycopersicon lycopersicon (L. ) Karsten] in nutrient solutions. Uptake and translocation of Fe-55 me diated by rhizoferrin in a short-term (10-h) experiment were at levels higher than those obtained by other microbial siderophores. Iron-rhiz oferrin acted similarly to the synthetic chelate FeEDDHA [ethylenediam ine di(o-hydroxyphenylacetic acid)] on remedy of chlorosis in a long-t erm (14-d) experiment.