中文摘要：

对细菌形貌的观测是研究细菌行为的基础,为了准确观测细菌的表面形貌,实验以大肠杆菌为研究对象,采用轻敲模式,在空气中利用原子力显微镜（AFM）对大肠杆菌进行扫描.实验优化了AFM的扫描参数以获得高质量的图像,并定量分析了大肠杆菌的表面形貌特征.结果表明,分辨率、扫描频率、setpoint值和I/P值对AFM图像的清晰度具有重要影响,参数选择不当都会使图像模糊或失真.实验得到的最佳扫描参数为：分辨率256,扫描频率2 Hz,setpoint值1.645V,I/P值0.3/0.4.所扫描的大肠杆菌长度为（985.2±76.8）nm,宽度为（751.5±74.7）nm,高度为（168.4±39.3）nm.研究表明,AFM既可以定性表征微生物细胞的表面结构特征,也可以定量分析细胞的形貌参数,这为深入研究微生物的生理活动和抗菌剂的作用机理提供了重要的依据和手段.

英文摘要：

The observation of the morphology of bacterial cell is fundamental for understanding the behavior of bacteria. To facilitate accurate observation, Escherichia coli, as a model bacterium, was imaged by atomic force microscopy （AFM） under trapping mode in air. AFM scanning parameters were optimized to obtain the high quality of the AFM image. In addition, the profiles of the bacterial morphology were quantitatively analyzed. The results show that the resolution, scanning frequency, setpoint and I/P gains have important effects on the quality of the AFM image, and the image would be obscure and fuzzy at inappropriate conditions. In this experiment, the optimal parameters are as follow： resolution 256, scanning frequency 2 Hz, setpoint 1.645 V, I/P gain0.3/0.4. The length, width and height of Escherichia coli are （985. 2± 76. 8） nm, （751. 5±74. 7） nm and （52. 8±10. 2） nm, respectively. This research reveals that AFM could not only analyze the surface features of microbe qualitatively, but also determine the size of the microbial cell quantitatively, which provide significant evidence and method to study the physiological activity of microbe and antibacterial mechanism of antibacterial agent.