Abstract: Concentrations of Cd in the plant of Solanum nigrum and in the rhizospheric soil of the plant growing in the Nanjing Qixia Pb-Zn Mine Area were determined,and Cd-resistant endophytic and rhizobacteria were isolated from the plant and characterized with respect to heavy metal resistance and production of plant growth-promoting factors.Results show that the soil was seriously polluted by Cd,with total Cd content averaging 19.74 mg·kg^-1.The Cd bioaccumulation coefficient of the stem and leaf of the plant was 1.21-9.65 and 0.65-4.76,respectively,which suggests that the plant is highly capable of enriching Cd.A total of five Cd-resistant strains of bacteria were isolated from the plant and the rhizospheric soil of the plant,Strain AR1 from the root,Strain AY1 from the leaf and Strains BGJ4 and CGJ1 from the rhizospheric soil.Phylogenetic analysis based on 16S rDNA sequencing reveals that the 5 Cd-resistant strains all belonged to the genus of Bacillus,capable of producing IAA and iron carriers.Strain AR1 could even survive and grow well in the medium containing 30 mg·kg^-1 of Cd²⁺.Rapeseed plants growing in vermiculite contanining 1.5 mg·kg^-1 of Cd²⁺,were found to increase roots growth after inoculation with the isolates AR1,AY1,and BGJ4.All the findings indicate that Cd-resistant bacteria producing IAA and siderophores in S.nigrum may be used for plant growth promotion and bacteria-assisted phytoremediation of heavy metal-contaminated soil.

Key words: Solanum nigrum, cadmium-resistant bacteria, growth-promoting, phytoremediation