Isolation,Identification And Biosorption Of Cadmium-Resistant Microbes From Soils

Heavy metal pollution is a serious problem in China. At present, the area of cultivated land polluted by Cd, Cr, Pb and other heavy metal is nearly 20 million hm2, about 1/5 arable land. Decreased harvest of crops by heavy metal pollution happens each year, the direct economic loss is more than 20 billion yuan. Agricultural safety and health events caused by the heavy metal pollution often occur, it has become the most important factor of human health and the social stability. Heavy metal pollution has been the worldwide concern. Every country attach great importance to study contaminated soil remediation and microbial remediation has been taken more notice. There is great need to screen and find microbial strains with high adsorption capacity and selective adsorption for microbial adsorbent development for controlling heavy metal pollution The study on ability and mechanism of adsorption provides important theory evidence for the chemical and genetic manipulations of biological adsorbent, as well materials for the construction of engineered microbes.8 high tolerance and high accumulation bacterial strains was screened and isolated from the soils of mines in Xichang,Sichuan province, In addition to using physiological and biochemical methods,16S rDNA molecular biology techniques had been used to identify the classification and strains of bacteria. Quantitative analysis of adsorption of the strains for heavy metals Cd2+ had been done, as well the determination of the tolerance to other heavy metals. Finally, plasmid preparation, restriction enzyme digestion and plasmid elimination experiments was used to study the tolerance and adsorption mechanism of heavy metals by these Cd2+ resistant strains.Main results:1. The 8 screened strains was able to grow at Cd2+ concentration of above 400mg/L in liquid nutrient medium and 800-1200mg/L on agar plate.2. The 8 strains had all been identified to be Pseudomonas putida.3. The strains could grow well at low concentration of Cd2+. Stationary phase starts on 10h on 25mg/L of Cd2+ and 14h on Omg/L of Cd2+4. The 8 strains had different adsorption abilities on Cd2+. CD5 was the highest with adsorption rate of 90.04% and adsorbance of 2.70mg (30ml),the contol strains was the lowest.5. The Strains was also tolerant for Pb2+,Zn2+,Cu2+,Ni2+,Mn2+, however lower than Cd2+.6. Plasmid could be extracted from all the 8 strains, the further study was needed.