Plant growth promoting rhizobacteria and their role in remediation of heavy metal contaminated soils

The using of plant growth promoting rhizobacteria in order to biological remediation and/or improvement the efficiency of other bioremediation methods of heavy metals contaminated soils has great advantages such as environmental friendly، low cost compared to physical and chemical remediation methods of metal contaminated soils، promotion of soil fertility، raise the biodiversity and etc.. Because of their tolerance to heavy metals، this rhizobacteria are able to adsorb or absorb metal pollutants and also can reduce metals to less toxic forms and thus remediate or immobilize metal. Furthermore، plant growth promoting rhizobacteria have the ability to enhance the plant growth on metal contaminated soils through various mechanisms such as fixation of atmosphere N2، phosphate solubilization، secret of Fe-chelating siderophores، and production of growth promoting hormones like auxin and gibberellin and prevention of excessive synthesis of ethylene by enzyme ACC-deaminase and thus، increase the phytoremediation efficiency of these soils. Hence، in this study، we have a brief review on the role of plant growth promoting rhizobacteria in remediation of heavy metal contaminated soils and also their effect on improve the phytoremediation efficiency of metal pollutants