Phytoremediation of metals from fly ash through bacterial augmentation

Different combinations of four bacterial strains isolated from fly ash were used by us to study their impact on phytoextraction of metals from fly ash by Brassica juncea grown in fly ash amended with farm yard manure (50:50 w/w). Out of 11 bacterial consortia, a combination of two strains i.e. Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C7) inoculated in the rhizosphere was found to enhance Pb accumulation maximally by 278%, Mn by 75%, Zn by 163%, Cr by 226% and Ni by 414% compared to control. It is possible that these bacteria, known for N-2 fixation, solubilization of phosphorus and uptake of micronutrient, could promote the plant growth resulting in higher accumulation of metals. However, a combination of four bacteria, namely Micrococcus roseus NBRFT2 + Bacillus endophyticus NBRFT4 + Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C4) was able to increase Cd uptake maximally by 237%. Further, the translocation of metal was invariably more from root to stem than from stem to leaf which was regulated by plant transport mechanism and metal mobility. Bacteria are known to excrete protons, organic acids, enzymes and siderophores to enhance the mobilization of metals which boosted the phytoextraction of metals from fly ash.