Role of rhizobacteria in phytoremediation of metal-impacted sites

Phytoremediation is an emerging and eco-friendly technology that has gained wide acceptance and is currently an area of active research in plant biology. A number of metal-hyperaccumulating plants have already been identified as potential candidates to phytoremediate metal-polluted soil. Various strategies have been successfully applied to generate plants able to grow in adverse environmental conditions and accumulate or transfer a number of metals. Recently, biotechnological approaches have opened up new opportunities concerning the application of beneficial rhizospheric and endophytic bacteria for improving plant growth, biological control, and heavy metal remediation from contaminated sites. Further, molecular approaches have been applied to improve the process of phytoremediation efficiently using a transgenic approach. The overexpression of several genes whose protein products are directly or indirectly involved in plant metal uptake, transport, and sequestration, or act as enzymes involved in the biodegradation of hazardous organic wastes, has opened up new possibilities in phytoremediation. This chapter is mainly focused on plant-microbe interactions to phytoremediate metal-contaminated sites and evaluate the progress made thus far in understanding the role of rhizospheric and endophytic bacteria in the phytoremediation of metal-contaminated sites and different phytoremediation technologies. In addition, we also discuss the use of genetic engineering to modify plants for enhanced efficacy phytoremediation strategies. These approaches will be helpful to develop phytoremediation technologies for large-scale application to remediate vast areas of metal-polluted sites.