Microbe-mediated remediation of heavy metal contamination

Heavy metal pollution has gained serious concern among scientific communities throughout the world in last few decades. The tenacious and recalcitrant property of this pollutants posed severe threat to the biosphere including humans. The use of living organisms to reduce the heavy metal contamination level has got holistic approach in the tune of economic and ecological benefits. The process of bioremediation is responsible for such removal/reduction of these contaminants from the ecosystem concerned. Among these, microbial remediation techniques such as use of algae, fungi or higher plants are the most convening innovative tools due to its cost-effectiveness and environment friendly approach endorsing sustainability. This technique helps to reduce the heavy metal accumulation to living system. A wide range of microbial participates in metal decontamination. Furthermore, among the existing microbial processes for decontamination (such as utilisation of indigenous microbial population, exogenous microbial input, use of microbial strain for pollutants sequestering, or immobilization) metal biotransformation is the prime technique. It includes processes such as adsorption, bio-sorption, cell-membrane transport (immobilization and solubilisation), complexation and ion-exchange. On the other hand, metal-microbe interaction involves processes such as bioleaching, bioaccumulations, biotransformation, biosorption and biomineralization, while metal resistance includes ex-polymer binding, siderophore, precipitation, complexation and biosurfactant. Previous studies have focused mainly on remediation techniques using single omics-approach (such as proteomics, genomics, metabolomics and transcriptomic), however the present review study addresses microbial- mediated bioremediation in integrative manner. Additionally, its execution in eco-friendly manner often becomes restricted due to lack of knowledge on factors regulating metabolism, growth and dynamics of diverse microbial communities involved in the contaminated environment. Therefore, the mechanism of environmental clean-up through microbial remediation needs thorough review and study on technological advancement for this in comprehensive process.