Role of rhizospheric bacteria in phytoremediation of heavy metal contaminated soil

Environmental pollution with toxic heavy metals is spreading throughout the world along with industrial progress. Copper, chromium, cadmium and nickel are few of the known heavy metals. Elevated level of heavy metals not only decrease soil microbial activity and crop production but also threatens human health through the food chain. Rhizoremediation is emerging as a potential cost effective solution for the remediation of heavy metal-contaminated soils in opposition to the conventional chemical and physical remediation technologies that are generally too costly and often harmful to soil characteristics. Rhizosphere plays a significant role in phytoremediation of heavy metals contaminated soil in which microbial population are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes. This paper reviews the important beneficial plant-microbe interaction that promote plant health and development. Role of rhizospheric bacteria that may promote plant growth by producing siderophore, synthesizing phytohormones and enzymes has also been discussed. The role of transgenic plants, genetically engineered microbes and tolerance of plants to heavy metals in stress environment for enhancing phytoremediation is also explained.