| In the world, especially in developing countries, cadmium pollution has become a serious environmental pollution phenomenon. Because of the cadmium property can soluble in water, the transter of cadmium in soil and organisms is becoming more and more frequent. Because it has not ability disposal of the cadmium pollution in natural environment, and bring great harm to human beings and animal health. In recent years, advancing the application of microbial bioremdation in environmental, more and more cadmium resistant microorganisms were screened from variety of environmental, and widely application in remediation of cadmium contaminated soil and wastewater. In this study, a cadmium tolerant strain was screened from heavy-contaminated soil in LiuYang and XiangXi (Fenghuang county, Guzhang County, Luxi county), China. Results were described in the following:(1) We use the pure culture method to obtain an cadmium tolerant actinomycete from cadmium-contaminated soil (Cadmium content,20.63 mg·g-1). Identified as a member of Streptomyces sp. base on morphology observation, physiological biochemical characteristics, analysis of 16S rDNA sequence, and phylogenetic tree and named Streptomyces sp. CdTB01. The maximum cadmium tolerant concentration of Streptomyces sp. CdTB01 is 45 mmol/L in PDA liquid medium. In addation, it is also can grow in the NA, Czapek-Dox and PDA solid medium containing 50 mmol/L Cd2+ after subcultured for 20 generations. Those results show that this isolater has a strong ability of tolerance to cadmium and genetic stability.(2) Using potato sucrose medium as the final culture medium through method of measuring cell dry weight, and the maximum tolerant concentration of Zn2+, Pb2+, Cu2+, Ni2+, Co2+, Mn2+, Cr6+ is 10.0,6.0,8.0,5.0,3.0,7.0,0.5 mmol/L, respectively, in potato sucrose solid medium.(3) Drug susceptibility test results show that the strain CdTB01 most sensitive to erythromycin(15 ?,g), neomycin(30?g)and chloramphenicol(30 ?g), followed by amikacin (30 ?g), novobiocin (30 ?g), tetracycline (30 ?g), streptomycin (10 u.g) and Polymyxin B (300 U), but to ampicillin (10 ?g), penicillin (10 IU) and nalidixic acid (30 ?g) is not sensitive.(4) The optimal growth conditions for Streptomyces sp. CdTB01 were determined as follows:fluid volume,90 mL/250 mL; temperature,30?; pH,6.0; NaCl concentration,0; inoculation amount,8.0%. Under the optimum growth conditions, the adsorption rate of Cd2+ for Streptomyces sp. CdTB01 was 8.80% and 17.75% respectively in a solution containing Cd2+concentration of 1000 mg/L.(5) The optimum Cd2+adsorption condition of Streptomyces sp. CdTB01 wet cell were determined as follows:temperature,30?; pH,8.0; NaCl concentration,1.0%; Cd2+ concentration,500 mg/L. The adsorption rate of Cd2+ is 44.78% under the above conditions. The optimum Cd2+adsorption condition of Streptomyces sp. CdTB01 dry cell were determined as follows:temperature,30 ?; pH,9.0; NaCl concentration,0; Cd2+ concentration,100 mg/L. The adsorption rate of Cd+ is 70.45% under the above conditions. The dosage of dry cell is 70.45 mg/g for Cd2+ adsorption.(6) The completed genome sequence of Streptomyces sp. CdTB01 was performed using single molecular sequencing technology with the PacBio? RS ? system and genome plot was acquired. The results of function annotation showing its has 31 genes employeed in cadmium stress response, and of these 2 SmtA gene,2 cysteine synthase B gene,5 P-type ATPase gene,9 ArsR gene,9 other heavy metal ions transporter gene,4 cadmium protein gene.The above results showed that Streptomyces sp. CdTB01 have a strong ability of cadmium adsorption,and has the potential application to the environmental remediation of Cd pollution. However, the mechanism of the cadmium resistance of Streptomyces sp. CdTB01 remains to be further studied. |
PDF Full Text Request