Chemical Structure and Biological Activity of A Siderophore Produced by Rhizopus arrhizus

Abstract

Abstract Rhizopus arrhizus grown on low‐Fe medium produces a siderophore, the chemical structure of which was determined by means of 1 H nuclear magnetic resonance (NMR), 13 C NMR, and circular dichroism spectroscopy. The siderophore was identified as N 1 ,N 4 ‐bis(1‐oxo‐3‐hydroxy‐3,4‐dicarboxybutyl)‐diaminobutane, chemically identical to rhizoferrin produced by Rhizopus microsporus . Growth promotion of R. arrhizus by several unferrated chelates in Fe‐limited medium was studied in microtitration plates. The impact of rhizoferrin was much more pronounced than the effect of other siderophores. This growth promotion was used as a bioassay for the detection of rhizoferrin. Purified Fe‐rhizoferrin was found to be a very efficient Fe source for tomato plants [ Lycopersicon lycopersicon (L.) Karsten] in nutrient solutions. Uptake and translocation of 55 Fe mediated by rhizoferrin in a short‐term (10‐h) experiment were at levels higher than those obtained by other microbial siderophores. Iron‐rhizoferrin acted similarly to the synthetic chelate FeEDDHA [ethylenediamine di( o ‐hydroxyphenylacetic acid)] on remedy of chlorosis in a long‐term (14‐d) experiment.