Phytoremediation potential of rhizobacterial isolates from Kans grass (Saccharum spontaneum) of fly ash ponds

Kans grass (Saccharum spontaneum) is a weed species that is frequently found in many heavy metal-enriched waste dumps including fly ash pond sites. In this study, among a collection of phosphate-solubilizing bacterial strains isolated from the rhizosphere of Saccharum spontaneum present in the abandoned ash pond site of Mejia Thermal Power Station (MTPS-DVC), three strains were characterized for their plant growth-promoting abilities. The isolates identified as Bacillus anthracis strain MHR2, Staphylococcus sp. strain MHR3 and Bacillus sp. strain MHR4 had phosphate solubilization indices of 2.86, 2.31 and 2.40 and they produced soluble phosphates of 700, 600 and 640 mg l⁻¹, respectively, in 4 days. In all the PSBs, pH significantly decreased, indicating the production of various organic acids. They showed other plant growth-promoting features like production of ammonia, siderophore, hydrocyanide and IAA. All of them were resistant to multiple heavy metals and antibiotics. Dry and fresh weight and shoot and root lengths of Brassica juncea L. increased in the presence of these isolates in pot cultures. The strains also increased phytoextraction ability of plants by enhancing the metal accumulation in plant tissues. Thus, the isolated indigenous and stress-adapted rhizobacteria may serve as potential biotechnological tool for the successful ecorestoration of various metal-contaminated sites.