Discovery of Virus

The discovery of viruses is a gradual process. In 1884, Charles Chamberland discovered that the agent responsible for rabies could pass through a porcelain filter that could block bacteria. At that time, any disease-causing agent was called a virus, so the terms “filterable virus” and “non-filterable virus” were used.

In 1892, Dmitri Ivanowski discovered that the agent responsible for tobacco mosaic disease could not pass through the same filter, but the bacteria-free filtrate could still cause the disease. This suggested the existence of a new type of infectious agent that was much smaller than bacteria.

The discovery of viruses is often credited to Wendell Stanley, who in 1935 purified the filterable agent that causes tobacco mosaic disease and crystallized it.

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He found that the crystals contained only proteins and nucleic acid. This discovery provided strong evidence that viruses are distinct from bacteria and other living organisms.

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Dmitri Ivanowski

Structure of Virus

A virus is a tiny particle that can infect living cells. It consists of two main parts:

• Genome: The genome is the genetic material of the virus, which can be either DNA or RNA. The genome encodes the instructions for making new viruses.
• Capsid: The capsid is a protein shell that protects the genome. The capsid is made up of many subunits called capsomeres.

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Virus Structure

Some viruses also have an envelope, which is a fatty membrane that surrounds the capsid. The envelope is derived from the host cell membrane when the virus buds out of the cell. The envelope contains proteins that help the virus attach to host cells.

Viruses are much simpler than bacteria. They do not have their own cells and cannot reproduce on their own. They must invade host cells and use the host cell’s machinery to reproduce.