Isolation And The Mechanism Of Cd～(2+) Adsorption Of A Cadmium-Tolerant Bacterium And Its Application In Restoring Cadmium-Contaminated Soils

Cadmium is considered as the most hazardous heavy metal with abroad applications value. Every year 3.9 ×10⁴ ton cadmium was released into the environment in the world . About 2.0×10⁷ha of plowland was contaminated by heavy metal in China. Cadmium compounds possesses the character of dissolving in liquid, bioaccumulation and toxicity, and is a kind of severe substances and caused carcinoma. Microorganism growing in cadmium-rich environment formed tolerance and resistance to cadmium to some extent. Adsorption and accumulation to heavy metal by cadmium-tolerant bacteria are one of available measures to treat cadmium - contaminated environment.A strain J5, that could resist and accumulate high concentration of cadmium, was isolated by acclimation of concentration gradient from the polluted soils around the smeltery in Anhui province, China. This bacteria could survive in liquid medium containing 40mmol/L Cd²⁺ and in solid bacteria medium containing 75mmol/L Cd²⁺. It was identified preliminarily as Pseudomonas sp., based on its physiological and biochemical characteristics and 16SrDNA series same source analysis.Strain J5 produced light black-green pigment. It could show light yellowish green in agar plate containing CdSO₄(from 1 to 12mmol/L Cd²⁺), ZnSO₄(from 1 to 2mmol/L Zn²⁺) or 1%MgCl₂. But the green pigment of strain J5 disappeared in agar plate containing 12mmol/L Cd²⁺. High concentration of heavy metal might restrain expression of J5 pigment. Strain J5 produced alkali and could accommodate pH change. It had sliminess and flocculation. The suitable growth concentration was 0.5% to 5% of NaCl. 10% of NaCl inhibited evidently the growth and cadmium tolerant capacity of strain J5. Strain J5 showed urease, catalase, fatty enzyme, arginine double - hydrolyze enzyme, phosphatase and phytate enzyme activity. The toxicity order to strain J5 was measured by 0.2mmol/L heavy metal ions(0.02 mmol/L Ag⁺), as follows:...