Detection and Characterization of Antibacterial Siderophores Secreted by Endophytic Fungi from .

Endophytic fungi from orchid plants are reported to secrete secondary metabolites which include bioactive antimicrobial siderophores. In this study endophytic fungi capable of secreting siderophores were isolated from , a medicinal orchid plant. The isolated extracellular siderophores from orchidaceous fungi act as chelating agents forming soluble complexes with Fe. The 60% endophytic fungi of produced hydroxamate siderophore on CAS agar. The highest siderophore percentage was 57% in (CAL1), 49% in (CAR12), 46% in (CAR14) by CAS liquid assay. The optimum culture parameters for siderophore production were 30 °C, pH 6.5, maltose and ammonium nitrate and the highest resulting siderophore content was 73% in . The total protein content of solvent-purified siderophore increased four-fold compared with crude filtrate. The percent Fe scavenged was detected by atomic absorption spectra analysis and the highest scavenging value was 83% by . Thin layer chromatography of purified siderophore showed a wine-colored spot with R value of 0.54. HPLC peaks with Rs of 10.5 and 12.5 min were obtained for iron-free and iron-bound siderophore, respectively. The iron-free siderophore revealed an exact mass-to-charge ratio (/) of 400.46 and iron-bound siderophore revealed a / of 453.35. The solvent-extracted siderophores inhibited the virulent plant pathogens , that causes bacterial wilt in groundnut and pv which causes bacterial blight disease in rice. Thus, bioactive siderophore-producing endophytic can be exploited in the form of formulations for development of resistance against other phytopathogens in crop plants.