The Application Of Atomic Force Microscopy In Bacteria

Atomic force microscopy (AFM), also known as scanning force microscopy, was developed initially as an instrument to study the surface topography of material. Because of its powerful functions developed, the AFM has been widely used in the field of biology and biomedicine, and substantial achievements have been obtained in recent years. Such rapid expansion of AFM applications in biology is due to the fact that AFM has several unique advantages compared with conventional microscopic techniques used for studying biological samples. For instance, most native biological molecules and cells can be imaged directly using AFM, without the sample pre-preparation of staining, shadowing or labeling. Three-dimensional (3D) reconstruction of the sample surface at molecular resolution is also achievable.Particularly, with the various applications offered by AFM, much attention has been attracted to study the microbial cell surfaces at high spatial resolution: (i) visualization of surface ultrastructure, (ii) measurement of surface force, and (iii) characterization of mechanical properties, especially of bacteria that has typical dimensions suitable for AFM. According to the studies in recent years, some difficulties associated with the sample preparation have existed. Thus, we carried out some premiary pilot studies by AFM, including bacterial sample preparation, effects of glutaraldehyde on several bacteria, autolysis of Bacillus subtilis, etc. The main research results are as follows:1. A more effective substrate — APTES-mica was found. In the experiment, APTES-mica is suitable substrate for AFM imaging Pseudomonas syringae pv. tabaci which could cause widespread and devastating tobacco wildfire disease. APTES-mica is also a desirable substrate for the sample preparation of another G~- bacterium Xanthomonas campestris pv. malvacearum and G~+ bacterium Bacillus subtilis.2. One of the aims of this thesis is to investigate the activity of glutaraldehyde on different bacterial cells using AFM. The observed surface...