Bioremediation Strategies for Mitigation of Heavy Metals: A Critical Review

In normal conditions plants require heavy metals for growth but their accumulation inn bioavailability form in soil and water has harmful effects on all biological systems. The increasing release of HMs from industrial discharge and other anthropogenic activities are threatening sustainable agricultural development, food supply and dairy industry. Under such conditions heavy metal (HM) stress is one of the most destructive abiotic stresses for plants. Anthropogenic activities are the main source of heavy metal (HM) accumulation. Industrial pollution of both water bodies and soil mainly consists of accumulation of Cr, Ni, Cu, Zn, Cd, Pb, Hg, and As. These heavy metals (HMs) non-biodegradable pollutants present in soil and water are not easy to metabolize and their concentration in soil and water increases with time. The conventional methods for removal of heavy metals from the environment involve high costs and are not eco-friendly. In contrast to this phytoremediation is an eco-friendly approach and it can be considered as an alternative to the traditional methods in terms of their cost-effectiveness and maximum recovery of the metal ions. Microbes have greater metal biosorption capacities and various mechanisms of metal sequestration. This review focuses on various aspects of phytoremediation including genetic engineering and microbe-assisted approaches.