Introduction To Viruses - Discovery

Discovery

In 1884 the French microbiologist Charles Chamberland invented a filter, known today as the Chamberland filter or Chamberland–Pasteur filter, that has pores smaller than bacteria. Thus he could pass a solution containing bacteria through the filter and completely remove them from the solution. In the early 1890s the Russian biologist Dmitri Ivanovsky used this filter to study what became known as the tobacco mosaic virus. His experiments showed that extracts from the crushed leaves of infected tobacco-plants remain infectious after filtration.

At the same time several other scientists proved that, although these agents (later called viruses) were different from bacteria, they could still cause disease, and they were about a hundred times smaller than bacteria. In 1899 the Dutch microbiologist Martinus Beijerinck observed that the agent multiplied only in dividing cells. Having failed to demonstrate its particulate nature he called it a "contagium vivum fluidum", a "soluble living germ". In the early 20th century the English bacteriologist Frederick Twort discovered viruses that infect bacteria, and the French-Canadian microbiologist Félix d'Herelle described viruses that, when added to bacteria growing on agar, would lead to the formation of whole areas of dead bacteria. Counting these dead areas allowed him to calculate the number of viruses in the suspension.

With the invention of the electron microscope in 1931 by the German engineers Ernst Ruska and Max Knoll came the first images of viruses. In 1935 American biochemist and virologist Wendell Meredith Stanley examined the tobacco mosaic virus and found it to be mostly made from protein. A short time later, this virus was separated into protein and RNA parts. A problem for early scientists was that they did not know how to grow viruses without using live animals. The breakthrough came in 1931, when the American pathologist Ernest William Goodpasture grew influenza and several other viruses in fertilised chickens' eggs. Some viruses could not be grown in chickens' eggs, but this problem was solved in 1949 when John Franklin Enders, Thomas Huckle Weller and Frederick Chapman Robbins grew polio virus in cultures of living animal cells. Over 5,000 species of virus have been discovered.