Bioremediation of Cr (VI), Fe, and other heavy metals (HMs) through plant-microbes interaction is one of the efficient strategies due to its high efficiency, low cost, and ecofriendly nature. The aim of the study was to isolate, characterize, and assess the potential of rhizospheric bacteria to enhance growth and metal accumulation by the chromium hyperaccumulator Vetiveria zizanoides. The bacterial strain isolated from mine tailings was identified to be Bacillus cereus (T1B3) strain exhibited plant growth-promoting traits including, 1-aminocyclopropane-1-carboxylate deaminase, indole acetic acid, and siderophores production, nitrogen fixation, and P solubilization. Removal capacity (mg L) of T1B3 strain was 82% for Cr (100), 92% for Fe (100), 67% for Mn(50), 36% for Zn (50), 31% for Cd (30), 25% for Cu (30), and 43% for Ni (50) during the active growth cycle in HM-amended, extract medium. Results indicate that inoculating the native V. zizanioides with T1B3 strain improves its phytoremediation efficiency of HMs. The mineralogical characteristics of chromite ore tailings and soil were also confirmed by X-ray diffraction, Fourier Transform Infrared, scanning electron microscope-energy dispersive spectroscopy analysis.

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Rock Phosphate (RP) is a natural phosphorus source which can be an alternative to chemical fertilizers; but unfortunately, we lack technologies to make it applicable in alkaline soils. Therefore the aim of this work was to study the effects of phosphorous solubilizing fungus Pleurotus ostreatus on rock phosphate solubilization and its effect on growth of Zea mays L. incorporated with brewery sludge. The activity of the selected strain indicates the formation of the halo zone supplemented with rock phosphate. The maximum concentration of soluble phosphorus (P) was found at the 9th day of incubation in Pikovskaya's broth containing rock phosphate as P source. The inoculation of P. ostreatus with RP and brewery sludge significantly increased the root length (49%), shoot length (27%), root fresh weight (20%), root dry weight (46%), shoot fresh weight (89%), shoot dry weight (87%), chlorophyll content (79%) and nutrient accumulation, i.e., P (2.13), K (4.48), Ca (134.21), Mg (38.09), Cu (1.70), Mn (5.15), Zn (12.08), S (78.25) times greater than control in Zea mays L. The phosphatic residues after microbial solubilization showed structural and elemental changes confirmed by SEM and FE-SEM attached with energy-dispersive X-ray. The XRD and FTIR pattern shows that the mineral constituent of the treated sample signifies the proper P solubilization. Though few reports are available on P. ostreatus but biosolubilization with rock phosphate in the presence of brewery sludge is not yet reported. Overall, these findings suggest a possible application of the abundant waste materials on the sustainable growth of the plants.

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