一株代尔福特菌的分离及其对Cd吸附机制研究

Isolation and Cd adsorption mechanisms of Delftia sp.M6 strain

微生物修复Cd污染技术的关键是获得对Cd具有较高耐性和较强固持能力的菌株,而微生物的修复效果与其对Cd的固持机制密切相关。本研究从重金属污染土壤中分离筛选出一株对Cd吸附率较高的菌株M6,采用批量吸附试验及扫描电镜(SEM)、傅里叶变换-红外光谱(FTIR)、X射线光电子能谱分析(XPS)等技术探究菌株对Cd的固持效果及机理。16S rRNA序列分析结果表明M6与代尔福特菌(Delftia sp.12,登录号KJ191561.1)的同源性达到100%,初步鉴定为代尔福特菌。在pH=7、温度为35℃、培养时间为48 h、初始Cd浓度为10 mg·L^(-1)时,M6对Cd吸附率最高,达71.8%。Cd浓度在10~100 mg·L^(-1)时,随着Cd浓度升高,M6对Cd吸附量逐渐增大,最大吸附量为36.73 mg·L^(-1)。通过测定M6胞内和胞外Cd含量发现,M6对Cd的固持作用包括胞内积累和胞外吸附。SEM扫描发现,吸附Cd后菌体表面出现沉淀物;FTIR结果发现菌体表面多种官能团参与Cd吸附过程。XPS结果表明Cd在菌体表面可能以Cd(OH)_(2)和CdCO_(3)形式存在。综上,菌株M6对Cd具有较强的耐性和较佳的固持能力,其固持机制包括胞内积累、胞外吸附和胞外沉淀。

The key to Cd bioremediation technology is obtaining Cd-resistant strains with high tolerance and strong fixation to Cd.The bioremediation effectivity is closely related to the mechanism of Cd fixation used by microorganisms.In this study,we isolated a Cd resistant bacterial strain M6 from heavy metals contaminated soil.We employed batch adsorption experiments,scanning electron microscopy,Fourier-transform infrared spectroscopy,X-ray photoelectron spectrometry,and other techniques to explore the Cd fixation capacity and mechanism of the M6 strain.It was found that M6 had the highest adsorption rate(71.8%)for Cd at pH 7,temperature of 35℃,and after 48 h of incubation with 10 mg·L^(-1)of initial Cd concentration.Adsorption capacity of Cd increased with concentration of Cd from 10 mg·L^(-1)to 100 mg·L^(-1),and the maximum adsorption capacity was 36.73 mg·L^(-1).The mechanism of Cd fixation by M6 included intracellular accumulation and extracellular adsorption.Scanning electron microscopy indicated precipitates on the cell surface of M6 after Cd adsorption.The Fourier-transform infrared spectra showed that various functional groups on the cell surface were involved in the adsorption of Cd by M6.X-ray photoelectron spectroscopy analysis revealed that Cd may existed on the surface of cells in the form of Cd(OH)_(2) and CdCO_(3).The results of 16S rRNA gene sequence analysis showed that M6 was 100%homologous to Delftia sp.12,and was preliminarily identified as Delftia sp..In conclusion,M6 has strong resistance to Cd and high fixation effect on Cd,and its fixation mechanism include intracellular accumulation,extracellular adsorption and extracellular precipitation.