Two cadmium-resistant strains of agricultural soil effective in remediating soil cadmium pollution

Cadmium (Cd) contamination in soil is particularly serious and its remediation is particularly important. Microbial passivation or immobilization is a feasible means for remediation of heavy metal contamination. In order to enrich the options for microbial remediation of soil Cd contamination and provide the possibility of efficient remediation, this study screened two Cd-tolerant strains (Bacterium IRHB1-74 and Microbacterium sp. SW615), examined their Cd removal performance, and application effects in potting experiments, and discussed the remediation mechanism from the level of microbial communities. The results revealed that the minimum inhibitory concentrations of the two strains were 100 and 50 mg.L-1, respectively. Scanning electron microscope, Energy dispersive spectrometry and Fourier transform infrared analyses of the two strains indicated that surface complexation and electrostatic attraction were the main mechanisms employed for Cd biosorption. The use of the two strains caused significant changes in the number of soil microbial community operational taxonomic units and in the abundance of Firmicutes, Verrucomicrobia, Patescibacteria, Bacteroidetes, and Acidobacteria in the soil, which in turn increased the soil pH, organic matter, available potassium content, and enhanced the urease, alkaline phosphatase, and catalase activities. The two strains effectively reduced the available Cd content in the rhizosphere soil of rape by 32.98%- 60.54%, and reduced the Cd content in the roots and stems of rape by 50.94%- 60.53% and 27.38%- 40.61% Cd, and it was confirmed by plant malondialdehyde content, superoxide dismutase activity and other physiological indicators.