the contaminated sites or precipitation of hydroxides [71]. Microbes mobilize the heavy metals from the
contaminated sites by leaching, chelation, methylation and redox tansformation of toxic metals. Heavy
metals can never be destroyed completely, but the process transforms their oxidation state or organic
complex, so that they become water-soluble, less toxic and precipitated [52]. Microorganisms use heavy
metals and trace elements as terminal electron acceptors or reduce them through the detoxification
mechanism, used for the removal of metals from the contaminated environment. Microorganisms
remove heavy metals through the mechanisms which they employ to derive energy from metals redox
reactions, to deal with toxic metal through enzymatic and non-enzymatic processes.