الملخص الإنجليزي
Toxic metals are increasingly accumulated in the environment as a result of human activities including mining, agriculture and chemical industries. Mercury is one of the major hazardous heavy metals with a high-risk potential for the environment and human health. It is ranked as the sixth out of the ten of the most hazardous elements in the environment, so its remediation has a high priority in bioremediation. In this study, Hg concentrations were measured in soil samples from two ancient copper mines at Wadi Al-Maidin and Wadi Lasail in the Sultanate of Oman. Mercury-tolerant microbes were isolated and identified, and their abilities to tolerate and/or extract Hg from the environment were investigated. Pseudomonas chengduensis and Bacillus cereus showed the highest abilities to remediate Hg at 50 ppm Hg with a removal rate of 99% after 48 hours at 30 °C and pH 7 and 35 °C and pH 7, respectively. In the group of isolated fungi, Eladia showed the highest remediation performance. It completely removes Hg from the experimental medium within 48 hours. All the other fungi have high removal rates between 97 and 99% after 48 hours of inoculation. Scanning* Electron Microscopy analysis suggests that Hg was removed via biosorption for most microbes except Enterobacter xiangfangensis that did not show any Hg particles on its surface but rather accumulates Hg in its cytoplasm. In conclusion, the isolated bacteria and fungi from heavily polluted ancient copper mining and processing sites are tolerant to Hg toxicity and can accumulate Hg on their surfaces or in their cytoplasm and they can, therefore, be considered as promising microorganisms for bioremediation.
