Remediation of environment niches such as soil, sediments and water amended with heavy metals
can be achieved through biologically encoded changes in the oxidation state. Bioremediation is the
microbe-mediated process for clearance or immobilization of the contaminants, including all possible
toxins like hydrocarbons, agrochemicals and other organic toxicants. But for inorganic toxic compounds
such as heavy metals, microbes are unable to simplify them into harmless compounds, and they should
be used according to their specialization for the type of contaminants. Thus the bioremediation strategy
for heavy metals depends on the active metabolizing capabilities of microorganisms. Several
microorganisms are known to require varying amounts of heavy metals as essential micronutrients for
growth and development. For example, Fe3+ is essentially required by all bacteria while Fe2+ is important