Impacts of chelate-assisted phytoremediation on microbial community composition in the rhizosphere of a copper accumulator and non-accumulator

Chelate-assisted phytoremediation has been proposed as an effective tool for the extraction of heavy metals from soil by plants. However, side effects of the addition of chelate to soil microbial community are usually neglected. We studied the potential effects of chelate (glucose and citric acid) amendment on phytoextraction of copper and microbial community composition in soil under laboratory conditions. A copper (Cu) accumulator, Elsholtzia splendens, and a non-accumulator, Trifolium repens, were grown on a sandy loam soil containing 317 mg kg 1 Cu. Microbial community compositions were analyzed by using polymerase chain reaction–denaturing gradient gel electrophoresis (PCR–DGGE). The results showed that the biomass of E. splendens grown with the chelate did not differ from that of the control. Addition of citric acid decreased the biomass of T. repens in comparison to that of glucose treatment. Application of glucose or citric acid significantly increased the extractable Cu concentration in planted and unplanted soils. Concentrations of Cu in the shoots of E. splendens were 2.6, 1.9 and 2.9 times of those of T. repens under no chelate, citric acid and glucose treatments, respectively. PCR–DGGE fingerprint analysis revealed that there were negative correlations between bacteria diversity and NH4NO3 extractable Cu under glucose or citric acid treatment. It was indicated the amendment of glucose to the plant T. repens increased the bacteria diversity in soil as compared to that in soils of non-chelate treatment. The above results indicated chelate addition facilitated phytoremediation of soil Cu and did not have a negative effect on microbial community.