Characterization and Fungal Inhibition Activity of Siderophore from Wheat Rhizosphere Associated Acinetobacter calcoaceticus Strain HIRFA32

Acinetobacter calcoaceticus HIRFA32 from wheat rhizosphere produced catecholate type of siderophore with optimum siderophore (ca. 92 % siderophore units) in succinic acid medium without FeSO4 at 28 A degrees C and 24 h of incubation. HPLC purified siderophore appeared as pale yellow crystals with molecular weight [M+1] m/z 347.18 estimated by LCMS. The structure elucidated by H-1 NMR, C-13 NMR, HMQC, HMBC, NOESY and decoupling studies, revealed that siderophore composed of 2,3-dihydroxybenzoic acid with hydroxyhistamine and threonine as amino acid subunits. In vitro study demonstrated siderophore mediated mycelium growth inhibition (ca. 46.87 +/- A 0.5 %) of Fusarium oxysporum. This study accounts to first report on biosynthesis of acinetobactin-like siderophore by the rhizospheric strain of A. calcoaceticus and its significance in inhibition of F. oxysporum.