Bioremediation of heavy metal–polluted environments by non-living cells from rhizobial isolates

Abstract

Rhizosphere bacteria, for example, rhizobia, can play several roles, and one of the most important, the protection of plant roots against toxic conditions and other environmental stresses. In this work, the action of Cu2+ and Cr6+ on cell growth and EPS production of four strains of rhizobia, Rhizobium tropici (LBMP-C01), Ensifer sp. (LBMP-C02 and LBMP-C03), and Rhizobium sp. LBMP-C04, were tested. The results confirmed the strong effect of Cu2+ and Cr6+ on bacterial exopolysaccharides (EPS) synthesis, and how cells can adsorb these metals, which may be a key factor in the interactions between rhizosphere bacteria and host plants in heavy metal–contaminated soils. Here, we emphasize the importance of proving the potential of treating bacterial cells and their extracellular EPS to promote the bio-detoxification of terrestrial and aquatic systems contaminated by heavy metals in a highly sustainable, economic, and ecological way.