Eubacterial Siderophores and factors modulating their production

Abstract

Siderophores are low-molecular-weight ligands produced by bacteria, fungi and plants to solubilize and take up iron. Iron is essential for the growth and development of almost all living organisms and acts as a catalyst in some of the most fundamental enzymatic processes, including oxygen metabolism, electron transfer and deoxyribonucleic acid (DNA)/ribonucleic acid (RNA) synthesis. However, despite its abundance on earth, iron is biologically unavailable in most environments as it aggregates into insoluble oxy-hydroxide polymers. Hence, to acquire this iron from natural ecosystems, bacteria have evolved multiple parallel pathways, the most important being siderophore production. This study was aimed at studying the incidence of siderophore-producing bacteria in the two coastal ecosystems of Goa: sand dunes and mangroves. The two isolates TMR2.13 and NAR38.1 selected for the study were identified as Pseudomonas aeruginosa and Bacillus amyloliquefaciens, respectively. Sodium benzoate was found to have a remarkable effect on siderophore production in P. aeruginosa TMR2.13 and increased iron demand of the organism as compared to the metabolism of simple substrates such as glucose. Studies were further carried out with B. amyloliquefaciens NAR38.1 to understand the effect of the presence of both biotic and abiotic metals in the growth medium. The presence of metals showed a varied effect on growth and siderophore production with increase in production of siderophores in the presence of zinc, cobalt, manganese, lead and aluminium which can be exploited in phytoremediation.