Bioaccumulation of Heavy Metals by Bacteria Isolates from Mambilla Mining Site, Nguroje, Taraba State, Nigeria

V.S. Tatah, I.N.E. Onwurah, O. Otitoju, O.E. Yakubu and L.M. Ayantse

Background and Objective: Increased mining activities globally have continued to be one of the major anthropogenic sources of environmental pollution by heavy metals. Microorganisms thriving in these sites have evolved several genetic mechanisms that enable them to adapt and survive. This study aimed at determining heavy metal bioaccumulation by bacteria isolates from a mining site. Materials and Methods: Five heavy metals resistance bacteria were isolated from a heavy metal polluted soil in the Mambilla mining site, biochemically characterized, identified and named MAMI 1, MAMI 2, MAMI 3, MAMI 4 and MAMI 5. Heavy metals bioaccumulation by the isolates was determined using ICP-MS. Results: Heavy metal quantification showed significant (p<0.05) deposition of Cd, Pb, Hg as and Zn in the soil at the mining site at 100, 200, 1.82, 10 and 300 mg kg^–1 concentrations, respectively compared to the control. MAMI 3 had the highest in situ bioaccumulation (20.30±0.28 mg kg^–1) of cadmium, followed by 18.35±0.21, 12.25±0.07, 10.25±0.35 and 8.15±0.07 mg kg^–1 for MAMI 5, MAMI 4, MAMI 2 and MAMI 1, respectively. There was no significant difference (p>0.05) in, in situ Pb bioaccumulation of MAMI 3 (50.20±0.14 mg kg^–1) and MAMI 5 (50.35±0.07 mg kg^–1), however, their bioaccumulation was significantly different (p<0.05) from those of MAMI 1 (20.65±0.21mg kg^–1), MAMI 2 (20.95±0.21 mg kg^–1) and MAMI 4 (43.55±0.35 mg kg^–1). All isolates showed low As and Hg bioaccumulation, however, they all had a very high accumulation of Zn in the order MAMI 3 (150.08±0.28 mg kg^–1) > MAMI 5 (145.70±0.4 mg kg^–1) > MAMI 4 (120.50±0.42 mg kg^–1) > MAMI 1 (100.20±0.14 mg kg^–1) and MAMI 2 (98.71±0.43 mg kg^–1). Conclusion: Bacteria isolates from the Mambilla mining site in this study, demonstrated high resistance and bioaccumulation of heavy metals, hence they can be explored for the bioremediation of heavy metals polluted sites.

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