Root associated iron oxidizing bacteria increase phosphate nutrition and influence root to shoot partitioning of iron in tolerant plant Typha angustifolia

Typha angustifolia is a heavy metal tolerant plant that grows in a uranium mine tailings highly contaminated with iron. In this study three iron oxidizing microbes (FeOBs) isolated from Typha rhizoplane were investigated for their role in plant growth promotion (PGP). Their effect on iron nutrition in Typha under iron replete and excess condition was also evaluated. The PGP activities of the FeOBs were studied by measuring their influence on plant growth. To investigate the mechanism of growth promotion their ability to solubilize phosphate, and to produce Indole acetic acid and siderophores were studied. The influence of the FeOBs on root to shoot partitioning of iron was tested by measuring total iron content in roots and shoots treated with microbes. The FeOBs were named as Paenibacillus cookii JGR8, (MTCC12002), Pseudomonas jaduguda JGR2 (LMG25820) and Bacillus megaterium JGR9 (MTCC12001). The siderophore producers, influenced iron accumulation in the plant root. Additionally P. pseudoalcaligenes JGR2 increased shoot iron content overcoming the root- shoot barrier that allows Typha to exclude metals from its shoot. Among the PGP mechanisms tested, ability to solubilize phosphate appeared to be most significant for increasing the plant biomass. FeOBs that produce siderophore increased iron content in plant and therefore can be of immense biotechnological importance. However Biomass increase was directly correlated with increased phosphate acquisition and not with enhanced iron accumulation in Typha.