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Toxic metals bioremediation potentials of Paenibacillus sp. strain SEM1 and Morganella sp. strain WEM7 isolated from Enyigba Pb–Zn mining site, Ebonyi State Nigeria

Abstract Heavy metal contamination is a serious environmental and ecological problem currently facing many countries. Discovering a novel biological means of detoxifying environments contaminated with these heavy metals is an urgent necessity. More so, an efficient bio-remediating agent from biological sources would be cost effective, climate change friendly and easily accessible with less negative effects on the environment. We report a novel study on heavy metals’ tolerant and bioremediation potentials of Penibacills sp. Strain SEM1 and Morganella sp. Strain WEM7 isolated from Enyigba Pb–Zn mining site, Ebonyi State, Nigeria. The result revealed that the bacteria isolates optimally thrived in media containing 5–15% of sodium chloride. The SEM1 showed capacity to tolerate lead, mercury and nickel up to 10,000 mg/l, up to 1400 mg/l for cadmium and up to 2500 mg/l each of copper and zinc. Additionally, WEM7 resisted zinc, copper and nickel up to 2500 mg/kg, mercury and cadmium up to 630 and 700 mg/kg respectively and more than 10,000 mg/kg of lead in both solid and liquid media. The 16S rRNA gene assay and phenotypic physiognomies of SEM1 and WEM7 strains fit in the genus Paenibacillus and Morganella respectively. The trend of heavy metals removal by SEM1 is as follows: Ni > Pb > Hg > Cu > Zn > Cd (97.62, 96.84, 90, 86.36, 84.85, 70%) and that of WEM7: Cu > Ni > Pb > Hg > Zn > Cd (100, 98.64, 97.48, 93.33, 80.85, 68.42%). Our investigation revealed that the isolates, SEM1 and WEM7 are moderately halophilic, metalophiles and could provide exceptional novel tool for mercury, lead, cadmium, nickel, copper and zinc bioremediation in contaminated environments.