Insights into the Status of Heavy Metal Resistant Rhizobacterial Communities in the Heavy Metal Contaminated Sites

Anthropogenic activities viz. modern agricultural practices, industrialization and mining have long term detrimental effects on environment. All these factors lead to the increase in heavy metal concentration in both hydrosphere and lithosphere. The extreme use of chemical fertilizers in agricultural field possesses a major threat to human and animal health and also causes various environmental hazards. The utilization of the chemical fertilizers can be reduced through biological aspects. Rhizosphere bacterial community is majorly involved in the plant growth and colonized in root zones of the plants with enhanced symbiotic relationship with plant community. These bacteria support the plant growth at normal and stressed conditions. These naturally occurring bacteria will pave a way to minimize the use of chemical fertilizers and hence in reducing the risk hazards. Plant-soil-root ecosystem is an important interface between soil and plants and also plays a significant role in the biosorption of heavy metals from contaminated soils. The rhizobacteria dwelling in this soil are known to affect heavy metal mobility and availability to the growing plant through the release of chelating agents, acidification, phosphate solubilization and redox changes, therefore having tremendous potentials to enhance the bioremediation processes. Bioremoval strategies with appropriate heavy metal-adapted rhizobacteria have received considerable importance. This chapter aims to reveal the sources of heavy metals and its effects on various life forms with special emphasis on PGPR assisted mechanisms for bioremoval of heavy metals from heavy metal implicated sites in the environment.