Introduction to viruses: Difference between revisions

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In 1884, French [[microbiologist]] [[Charles Chamberland]] invented the [[Chamberland filter]] (or Chamberland–Pasteur filter), that contains pores smaller than [[bacteria]]. He could then pass a solution containing bacteria through the filter, and completely remove them. In the early 1890s, Russian [[biologist]] [[Dmitri Ivanovsky]] used this method 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.<ref>{{harvnb|Shors|2017|p=6}}</ref>

At the same time, several other scientists showed that, although these agents (later called viruses) were different from bacteria and about one hundred times smaller, they could still cause disease. In 1899, Dutch microbiologist [[Martinus Beijerinck]] observed that the agent only multiplied when in [[cell division|dividing cells]]. He called it a "contagious living fluid" ({{langx|la|text= [[contagium vivum fluidum]]}})—or a "soluble living germ" because he could not find any germ-like particles.<ref name="x880">{{sfncite book | last=Howley | first=Peter M. | last2=Knipe | first2=David M. | last3=Enquist | first3=Lynn W. | title=Fields Virology: Fundamentals | publisher=LWW | publication-place=Philadelphia | date=2023-09-25 | isbn=978-1-9751-1251-6 |p page=4}}</ref> In the early 20th century, English [[bacteriologist]] [[Frederick Twort]] discovered viruses that infect bacteria,<ref>{{harvnb|Shors|2017|p=827}}</ref> and 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.<ref>{{cite journal | vauthors = D'Herelle F | title = On an invisible microbe antagonistic toward dysenteric bacilli: brief note by Mr. F. D'Herelle, presented by Mr. Roux. 1917 | journal = Research in Microbiology | volume = 158 | issue = 7 | pages = 553–554 | year = 2007 | pmid = 17855060 | doi = 10.1016/j.resmic.2007.07.005 | doi-access = free }}</ref>

The invention of the [[electron microscope]] in 1931 brought the first images of viruses.<ref>From ''Nobel Lectures, Physics 1981–1990'', (1993) Editor-in-Charge Tore Frängsmyr, Editor Gösta Ekspång, World Scientific Publishing Co., Singapore</ref> In 1935, American [[biochemist]] and [[virologist]] [[Wendell Meredith Stanley]] examined the tobacco mosaic virus (TMV) and found it to be mainly made from [[protein]].<ref>{{cite journal | vauthors = Stanley WM, Loring HS | year = 1936 | title = The isolation of crystalline tobacco mosaic virus protein from diseased tomato plants | journal = Science | volume = 83 | issue = 2143| page = 85 | pmid = 17756690 | doi = 10.1126/science.83.2143.85 |bibcode = 1936Sci....83...85S }}</ref> A short time later, this virus was shown to be made from protein and [[RNA]].<ref>{{cite journal | doi = 10.1126/science.89.2311.345 | vauthors = Stanley WM, Lauffer MA | year = 1939 | title = Disintegration of tobacco mosaic virus in urea solutions |journal = Science | volume = 89 | issue = 2311| pages = 345–347 | pmid = 17788438 |bibcode = 1939Sci....89..345S }}</ref> [[Rosalind Franklin]] developed [[X-ray crystallography|X-ray crystallographic pictures]] and determined the full structure of TMV in 1955.<ref name="pmid18702397">{{cite journal | vauthors = Creager AN, Morgan GJ | title = After the double helix: Rosalind Franklin's research on Tobacco mosaic virus | journal = Isis; an International Review Devoted to the History of Science and Its Cultural Influences | volume = 99 | issue = 2 | pages = 239–272 | date = June 2008 | pmid = 18702397 | doi = 10.1086/588626 | s2cid = 25741967 }}</ref> Franklin confirmed that viral proteins formed a spiral hollow tube, wrapped by RNA, and also showed that viral RNA was a single strand, not a double helix like DNA.<ref name="Johnson">{{cite journal |last1=Johnson |first1=Ben |title=Rosalind Franklin's contributions to virology |journal=Nature Portfolio Microbiology Community |date=25 July 2017 |url=https://microbiologycommunity.nature.com/posts/18900-rosalind-franklin-s-contributions-to-virology |access-date=7 January 2022 |language=en}}</ref>