Abstract
Background:Mercury is a toxic metal that is present in small amounts in the environment, but its level is rising steadily, due to different human activities, such as industrialization. It can reach humans through the food chain, amalgam fillings, and other sources, causing different neurological disorders, memory loss, vision impairment, and may even lead to death; making its detoxification an urgent task.Methods:Various physical and chemical mercury remediation techniques are available, which generally aim at: (i) reducing its mobility or solubility; (ii) causing its vaporization or condensation; (iii) its separation from contaminated soils. Biological remediation techniques, commonly known as bioremediation, are also another possible alternative, which is considered as cheaper than the conventional means and can be accomplished using either (i) organisms harboring themeroperon genes (merB,merA,merR,merP,merT,merD,merF,merC,merE,merHandmerG), or (ii) plants expressing metal-binding proteins. Recently, differentmerdeterminants have been genetically engineered into several organisms, including bacteria and plants, to aid in detoxification of both ionic and organic forms of mercury.Results:Bacteria that are resistant to mercury compounds have at least a mercuric reductase enzyme (MerA) that reduces Hg+2to volatile Hg0, a membrane-bound protein (MerT) for Hg+2uptake and an additional enzyme, MerB, that degrades organomercurials by protonolysis. Presence of bothmerA andmerB genes confer broad-spectrum mercury resistance. However,merA alone confers narrow spectrum inorganic mercury resistance.Conclusion:To conclude, this review discusses the importance of mercury-resistance genes in mercury bioremediation. Functional analysis ofmeroperon genes and the recent advances in genetic engineering techniques could provide the most environmental friendly, safe, effective and fantastic solution to overcome mercuric toxicity.
Highlights
For a long time, the term “heavy metals” had been widely used for metals associated with contamination and eco1874-0707/18 2018 BiotechnologyMicrobial Diversity of Mer Operon GenesThe Open Biotechnology Journal, 2018, Volume 12 57-toxicity
This review aims to cover all aspects related to the environmental biogeochemical cycle of mercury, the roles of mer genes in microbial adaptation to mercury, and potential bacterial remediation strategies of this toxic metal
Mercury usage should be restricted more to reduce its pollution. mer genes enable bacteria to convert the toxic organic or inorganic mercury forms to less toxic forms helping in mercury bioremediation as the most environmental friendly, safe and effective remediation technique
Summary
The term “heavy metals” had been widely used for metals associated with contamination and eco1874-0707/18 2018 BiotechnologyMicrobial Diversity of Mer Operon GenesThe Open Biotechnology Journal, 2018, Volume 12 57-toxicity. Toxic metals are stable and persistent environmental contaminants [2] Many metals such as mercury, cadmium, chromium, zinc, lead, copper, arsenic etc., used in different industries, are releasing its toxic ions and introducing it into the ecosystem leading to toxic effects, affecting humans, animals, plants, and microbial communities [3]. Mercury is a toxic metal that is present in small amounts in the environment, but its level is rising steadily, due to different human activities, such as industrialization. It can reach humans through the food chain, amalgam fillings, and other sources, causing different neurological disorders, memory loss, vision impairment, and may even lead to death; making its detoxification an urgent task
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