Interaction between microorganisms and chelators in plant based heavy metals removal systems

Heavy metals contaminated soils can be remediated by chemical¡ physical and biological methods. Phytoremediation is one of the bioremediation methods used to heavy metals contaminated soils and involves specific plant-based techniques for absorption¡ accumulation¡ elimination and stabilization of toxic metal pollutants. The efficiency of heavy metals extraction by plants used in this technology is dependent on factors such as amount of biomass produced by plant and metal elements bioavailability. Some microorganisms existing in plants rhizosphere such as plant growth promoting bacteria and mycorrhizal fungi cause increased plant growth and consequently accelerated elimination of soil metal pollutants. On the other hand¡ many rhizobacteria are resistant to heavy metals and by secretion of organic acids can solubilize unavailable forms of heavy metals and consequently increase their absorption by resistant plants. In this short review paper¡ we try to discuss the role of rhizospheric microorganisms in increased efficiency of heavy metals phytoremediation by plants.