以大气颗粒物中的高硅质矿物细颗粒——石英粉尘和重金属离子附载污染物Pb(Ⅱ)为实验材料, 人工制备载铅石英粉尘。 以16 g·L-1的载铅(Ⅱ)石英粉尘及不同浓度的PbCl2染毒大肠杆菌细胞, 观察染毒2 h后对机体的联合氧化损伤效应, 并探讨其对大肠杆菌表面基团及蛋白酰胺I带二级结构的影响。 结果表明, 与Pb(Ⅱ)、 载铅石英粉尘作用后, 大肠杆菌细胞活力降低, 胞内活性氧(ROS)及丙二醛(MDA)产生增多、 谷胱甘肽(GSH)含量下降, 引起细菌氧化应激水平的提高； 皮尔逊(Pearson)相关性分析显示载铅石英粉尘的细菌毒性与粉尘中Pb(Ⅱ)可交换态含量成正相关, 载带高浓度Pb(Ⅱ)的石英粉尘组胞内ROS/MDA水平与其单纯石英粉尘组和Pb(Ⅱ)组比较显著增加(p<005)； 重金属Pb(Ⅱ)、 载铅石英粉尘对大肠杆菌菌体表面基团的影响主要集中于磷酸二酯基团和表面多糖分子, 采用二阶导、 去卷积和谱线拟合技术对酰胺Ⅰ带特征峰(1 600～1 700 cm-1)进行分峰拟合后发现, 与Pb(Ⅱ)、 载铅石英粉尘(Q-Pb-0, Q-Pb-3)作用后, β-sheets/α-helices的比值由对照组的141分别降低到133, 127和122, 表明细菌表面蛋白质结构发生了变化, 从而可能影响了细菌的生理活动。 研究表明自由基所产生的氧化损伤可能是载Pb(Ⅱ)石英粉尘的一种重要毒性作用机制, 载带Pb(Ⅱ)的复合石英粉尘在致大肠杆菌机体氧化损伤效应方面二者存在一定的协同作用。

In this study, quartz dusts and Pb(Ⅱ), the high siliceous mineral fine particles and main heavy metal pollutants in atmospheric particulate matter, were used as experimental materials to prepare Pb coated onto quartz dusts. Experiments were carried out to examine the oxidative stress response of Escherichia coli to PbCl2 and 16 g·L-1 Pb(Ⅱ) coated onto quartz dusts, and to explore the effect on E. coli surface groups and protein amide Ⅰ band secondary structure. The reduction of cells viability, glutathione depletion with a concomitant increase in reactive oxygen species and malondialdehyde levels demonstrated that Pb(Ⅱ) and Pb coated onto quartz dusts induce oxidative stress leading to cytotoxicity in E. coli. Moreover Pearson correlation analysis showed that there existed significant positive correlation (p<005) between bacteria toxicity and Pb(Ⅱ) exchange state content in the dusts. Exposures to Pb coated onto quartz dusts produced significant increases vs. both single quartz dusts and Pb(Ⅱ) in ROS/MDA (p<005). The influence of Pb(Ⅱ), Pb coated onto quartz dusts on E. coli surface groups focused on phosphate ester groups and surface polysaccharide molecules, amide Ⅰ band characteristic peak (1 600~1 700 cm-1) were fitted by the second derivative, deconvolution and line fitting technology, found that protein amide Ⅰ band beta sheets/alpha helices ratio decreased obviously after infected, the ratio decreased from 141 to 133, 127 and 122, respectively, after effects of Pb (Ⅱ) and Pb coated onto quartz dusts(Q-Pb-0/Q-Pb-3), suggesting that the structure of bacterial surface proteins were changed, which may affect the physiological activities of the bacteria. The results indicate that the oxidative damage effect may be an important toxicity mechanism of Pb(Ⅱ) coated onto quartz dusts, in addition, exposure to Pb(Ⅱ) coated onto quartz dusts can cause association oxidative stress on E. coli than either material alone.