Discovery and Origin of Viruses

Do you "discover" something without actually being able to see it?

Yes, you can and that's exactly the way viruses were first discovered. The size of viruses is much less than bacteria, and therefore specific microscopes are required to detect them, however their existence was well-known before the invention of these microscopes.

Discovery and Origin of Viruses

They are so small they are visible only by using only an electron microscope. Before the invention of electron microscopes they were able to tell that viruses exist. What did they know? They had proven that microbes smaller than bacteria are the cause of disease.


Discovery of Viruses

Researchers made use of filters that were designed to eliminate the bacteria from the tissues infected. If bacteria caused the infection, then the filtered tissues would no longer be able of making others infected with the same. However, the tissues that were filtered were still infected. This suggests that something smaller than bacteria was responsible for the infection.


Scientists didn't actually discover viruses at first before the 30s. This was the time when the electron microscope was invented. It was in 1915 that English scientist Frederick Twort discovered bacteriophage, which are viruses which target bacteria. He observed tiny, crystal-clear spots inside bacteria colonies and speculated that something was killing the bacteria.


Tobacco Mosaic Viral under microscope


Tobacco Mosaic Virus. The mosaic virus from tobacco was among the first viruses identified. It was first observed using the aid of an electron microscope in 1935.


Origin of Viruses

What is the source of viruses? What caused the first viruses to develop? These questions aren't yet known with certainty. There are a variety of hypotheses that have been suggested. The two most popular theories are listed below. Both could be valid and help explain the origins of various viruses.


Small viruses began as nucleic acid , which originally came from living cells like bacteria.

Large viruses were parasitic cells within larger host cells. In time, the genes required to live and reproduce outside host cells disappeared.

Summary

Viruses were believed to be present before they were first discovered using microscopes using an electron microscope in the 1930s.

Many theories of the viral cause have been suggested