大肠杆菌IscA膜表面表达菌株在吸附水体重金属中的应用

为构建一种能够高效、同时吸附水中多种重金属离子的大肠杆菌,利用融合蛋白表达技术,首先将大肠杆菌前脂蛋白信号肽Lpp、膜蛋白OmpA的N端部分氨基酸和铁硫簇组装蛋白IscA的编码基因序列进行融合,构建pET-Lpp-OmpA-IscA表达载体,将此载体导入大肠杆菌BL21菌株.在IPTG诱导下,IscA蛋白可表达于细胞膜表面.然后对IscA膜表面表达菌株对重金属的吸附能力进行评估,包括测定最大吸附容量、绘制吸附浓度依赖曲线和时间依赖曲线,以及对菌株清除工业污水中重金属的性能进行初步探索.研究结果表明,与本底对照菌株相比,IscA蛋白在细胞膜表面表达能够使菌株对水中的Cu~(2+)、Ni~(2+)、Cd~(2+)、Pb~(2+)、As~(3+)、Co~(2+)、Hg~(2+)这7种重金属的吸附能力提高2～5倍不等,并且在pH为6～8范围内保持其吸附能力基本不变.此菌株能够在30 min内将各种重金属溶液中超标5倍的金属含量降低至最大允许排放浓度以下,并且对吸附的重金属具有不同程度的回收能力和菌株再生能力.此外,该菌株能够同时吸附工业污水中的多种重金属,有效降低各种重金属含量.因此,利用膜表面表达技术对大肠杆菌进行改造,成功提高了大肠杆菌对多种重金属的吸附能力,为利用微生物治理环境重金属污染提供了良好的应用前景.

Application of IscA surface-displayed Escherichia coli in bioadsorption of heavy metals in water

To construct an Escherichia coli strain with high adsorption capacity for multiple heavy metals, a pET-Lpp-OmpA-IscA vector that can express a fusion protein containing the N-terminal of prelipoprotein Lpp, membrane protein OmpA, and an iron-sulfur assembly protein IscA was constructed and transformed into E. coli BL21 strain. The IscA could be produced on the cell surface upon induction with IPTG. The adsorption of heavy metals by the strain with surface-displayed IscA was evaluated with respect to the maximal adsorption capacity, concentration response and time dependence; the ability of the strain to remove heavy metals from industrial wastewater was also assessed. The results show that IscA surface-displayed E. coli could adsorb 2-to 5-fold higher amount of heavy metals (Cu²⁺, Ni²⁺, Cd²⁺, Pb²⁺, As³⁺, Co²⁺, Hg²⁺) compared to the control strain, and the adsorption capability did not significantly get attenuated within the pH range of 6~8. water samples with heavy metals in a concentration exceeding the standard by 5-fold could be reduced to normal levels due to bioadsorption within 30 min. Several heavy metals adsorbed by this strain could be released for recycling with concomitant regeneration of the strain. Furthermore, this strain was able to simultaneously adsorb multiple heavy metals in industrial waste water, resulting in an effective decrease in the total heavy metal content. Thus, we successfully engineered an E. coli strain with improved heavy metal adsorption capacity using the cell surface-display approach. This may provide useful strategies for the development and optimization of microorganisms for bioremediation of heavy metal pollutants.