Hydroxamate type of Siderophore production by rhizobacterial strains isolated from root nodules of Vigna trilobata

Abstract

21 rhizobacterial strains were isolated from root nodules of Vigna trilobata (L-Verdc) plants raised in soils collected from geographically different areas in Andhra Pradesh, India. The identification of rhizobacteria was done by biochemical and by 16 S rDNA sequencing analysis along with accession numbers (Rhizobium sp. MRR 106, KC428655 and Rhizobium sp. MRR 123, KC503884). Detection of siderophore production by microorganisms in solid medium is the universal Chrome Azurol’ S (CAS). Agar plate assay method was used for this study. Out of 21 strains, only 7 showed the siderophore production. Of the 4 siderophore positive, two strains Rhizobium sp. MRR 106 and Rhizobium sp. MRR 123 are hydroxamate type and rest of them are catechol type. Siderophore production was observed at 24 h of incubation and it reached maximum at 144 h of incubation. Qualitative and quantitative estimation of hydroxamate type of siderophore production shows much difference along with iron concentrations up to 20 to 80 μM in Rhizobium sp. MRR 106 and Rhizobium sp. MRR 123. Various carbon and nitrogen sources greatly influenced the siderophore production. Among them, glucose (1%) and glycine (0.1%) were found to be the best for siderophore production.