Study of Siderophore Formation in Nodule-Forming Bacterial Species

Siderophores are potent ferric ion chelators produced by microbes like bacteria and fungi during iron stress. The objective of this study was to verify the siderophore-production in noduleforming bacteria and then to compare them with pure cultures of Rhizobium meliloti bacteria. It was achieved by inoculating nodule-forming bacteria in YEM media followed by Chrome Azurol Sulfonate (CAS) assay, a universal siderophore detection method. Formation of orange halos in blue agar plates confirmed the CAS assay. Comparison of diameter of halos with the orange halos of pure strain revealed that the former were less effective in siderophore production. The detergent HDTMA (Hexadecyltrimethylammonium bromide) also appeared to be toxic for some isolates as indicated by negligible growth of the culture. This specificity of different bacterial strains towards siderophore formation and further chelation can be used as a model for identification studies of many human pathogenic bacteria and further to find a classic microbial species for iron-related poisoning.