Electron Microscopy of Viruses

Abstract

Because most viruses are too small to be observed by light microscopy, electron microscopy (EM) is the method of choice for the direct visualization of viruses and viral proteins. To survive the high vacuum inside the microscope, biological samples have to be dehydrated and/or fixed (chemically or by using low temperatures). We describe the different techniques that allow the sample to be observed in the electron microscope, going from different kinds of single particle preparations such as negative staining, cryo-EM, and metal shadowing to the numerous sectioning techniques including the very new Cryo-EM of vitreous sections technique. We also mention the steps that take place after single particle imaging: Image analysis, 3D-reconstruction, and combination of the obtained EM data with data from other structural biology techniques. Most of the preparation techniques and the results that can be obtained are illustrated using images of adenovirus particles, adenovirus proteins, and adenovirus-infected cells.