Metal mobilization and production of short-chain organic acids by rhizosphere bacteria associated with a Cd/Zn hyperaccumulating plant, Sedum alfredii

Sedum alfredii, a cadmium (Cd) and zinc (Zn) hyperaccumulator at a mine located in Qu Zhou City, Zhejiang Province, China, can accumulate Cd and Zn exceeding 1,000 and 10,000 mg kg⁻¹, respectively in its shoot (dry weight) when growing under metal-contaminated habitats. Several strains of bacteria were isolated from the rhizosphere of S. alfredii thriving in different Pb/Zn mines in Hunan Province and Zhejiang Province, China, which can resist high levels of heavy metals. Among the different strains isolated, Burkholderia cepacia showed the highest ability in mobilizing Cd and Zn as well as resisting high concentrations of soluble Zn (500 mg L⁻¹). The soluble Zn concentration in the medium increased from 13 to 72 and 99% (p