Positive staining of Viruses


Positive staining of viruses is a technique that uses heavy metal salts, such as uranyl acetate and lead citrate, to create a contrast between the virus particles and the background. The virus particles appear dark on a light background, revealing their shape, size and structure. This technique is useful for studying the diverse morphologies of viruses from different environments.

Positive staining of viruses is similar to negative staining, which is another technique that uses heavy metal salts to create a contrast. However, in negative staining, the virus particles appear light on a dark background, while the background is stained by the metal salts. This technique is useful for studying the surface features of viruses, such as spikes and envelopes.

Both positive and negative staining are simple and rapid methods that do not require any fixation or embedding of the samples. They can be performed directly on the grids that are used for observing the samples under a transmission electron microscope (TEM). However, they have some limitations, such as sensitivity to light and carbon dioxide, which can affect the quality of the images. Also, they do not preserve the internal structures of the viruses, such as nucleic acids and proteins.

Positive and negative staining are complementary techniques that can provide different information about the viruses. By using both techniques, one can obtain a more comprehensive view of the viral morphology and physiology. For example, positive staining can show the size and shape of the virus particles, while negative staining can show the surface features and arrangement of the virus particles. Together, they can help identify and characterize different types of viruses.