But when a virus enters a cell (called a host after infection), it is far from inactive. By that description, a virus seems more like a chemistry set than an organism. Stanley shared the 1946 Nobel Prize- in chemistry, not in physiology or medicine-for this work.įurther research by Stanley and others established that a virus consists of nucleic acids (DNA or RNA) enclosed in a protein coat that may also shelter viral proteins involved in infection. But it lacked essential systems necessary for metabolic functions, the biochemical activity of life. They saw that it consisted of a package of complex biochemicals. Stanley and his colleagues, at what is now the Rockefeller University in New York City, crystallized a virus- tobacco mosaic virus-for the fi rst time.
Their demotion to inert chemicals came after 1935, when Wendell M. Because they were clearly biological themselves and could be spread from one victim to another with obvious biological effects, viruses were then thought to be the simplest of all living, gene-bearing life-forms. The initial interest in viruses stemmed from their association with diseases-the word “virus” has its roots in the Latin term for “poison.” In the late 19th century researchers realized that certain diseases, including rabies and foot-and-mouth, were caused by particles that seemed to behave like bacteria but were much smaller. They seem to vary with each lens applied to examine them.
It is easy to see why viruses have been diffi cult to pigeonhole. Finally, however, scientists are beginning to appreciate viruses as fundamental players in the history of life. The categorization of viruses as nonliving during much of the modern era of biological science has had an unintended consequence: it has led most researchers to ignore viruses in the study of evolution. First seen as poisons, then as life-forms, then biological chemicals, viruses today are thought of as being in a gray area between living and nonliving: they cannot replicate on their own but can do so in truly living cells and can also affect the behavior of their hosts profoundly. They were, and are, not alone.įor about 100 years, the scientifi c community has repeatedly changed its collective mind over what viruses are. Yet it is almost certain that they did not know exactly what a virus was. In an episode of the classic 1950s television comedy The Honeymooners, Brooklyn bus driver Ralph Kramden loudly explains to his wife, Alice, “You know that I know how easy you get the virus.” Half a century ago even regular folks like the Kramdens had some knowledge of viruses-as microscopic bringers of disease. Editor's Note: This story was originally published in the December 2004 issue of Scientific American.
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