Reaction of ferric iron by siderophore produced by a bradyrhizobium strain

Abstract

Ferric iron (Fe⁺³) chelating compounds, including siderophores produced by microorganisms, help in the Fe nutrition of plants. Dicotyledonous plants absorb Fe in the ferrous (Fe⁺²) form. The ability of siderophores produced by a Brady ‐rhizobium strain, a rhizosphere bacterium of groundnut (Arachis hypogaea), to reduce Fe⁺³ was tested. Two Fe⁺³ (⁵⁸Fe) binding fractions were separated from the culture supernatant of a Bradyrhizobium strain grown in an iron deficient medium. One of the fractions isolated reduced Fe⁺³ to Fe⁺², unlike the synthetic chelator ethylenediaminetetraacetic acid (EDTA). It has been proposed that Fe‐chelators supply Fe⁺³ to groundnut roots, and Fe⁺³ reduction to Fe⁺² and its uptake occurs at the plasmalemma. Since siderophores can reduce Fe⁺⁺⁺, they may help in Fe nutrition of groundnut plants better than chelators like EDTA. There is no evidence to indicated siderophore uptake by groundnut plants, but we have detected ethyl acetate insoluble Fe⁺³ reducing activity in the xylem sap of the plants.