Microbial allies: purified siderophore from Bacillus amyloliquefaciens D5 enhances Vigna radiata L. growth

Siderophores are specialized, low-molecular-weight molecules produced by microbes to chelate iron under limited availability, enhancing microbial survival and competitive advantage. In plant–microbe interactions, siderophores play a dual role: they deprive pathogens of essential iron and can trigger host defense responses, such as induced systemic resistance. In the present study, Bacillus amyloliquefaciens D5 was identified as a prolific siderophore producer, with the catecholate-type siderophore bacillibactin being purified using Amberlite XAD4 column chromatography. Spectral analysis revealed absorption maxima between 264–303 nm, characteristic of catecholate siderophores, and the concentration of the purified siderophores was determined to be 50 µg/mL. The efficacy of these purified siderophores was further evaluated in a plant growth promotion assay, where they significantly enhanced vegetative parameters and reduced the incidence of leaf spot disease. The findings underscore the dual functionality of siderophores in nutrient acquisition and pathogen suppression, highlighting its potential as a biostimulant or bioprotectant. This study provides critical insights into the mechanistic role of siderophores in plant–microbe interactions, paving the way for their application in sustainable agricultural practices and biotechnological innovations.