Editing Microorganism (section)

===19th century===
[[File:Albert Edelfelt - Louis Pasteur - 1885.jpg|thumb|upright=0.8|left|[[Louis Pasteur]] showed that Spallanzani's findings held even if air could enter through a filter that kept particles out.]]

[[Louis Pasteur]] (1822–1895) exposed boiled broths to the air, in vessels that contained a filter to prevent particles from passing through to the [[growth medium]], and also in vessels without a filter, but with air allowed in via a curved tube so dust particles would settle and not come in contact with the broth. By boiling the broth beforehand, Pasteur ensured that no microorganisms survived within the broths at the beginning of his experiment. Nothing grew in the broths in the course of Pasteur's experiment. This meant that the living organisms that grew in such broths came from outside, as [[spore]]s on dust, rather than spontaneously generated within the broth. Thus, Pasteur refuted the theory of [[spontaneous generation]] and supported the [[germ theory of disease]].<ref>{{cite journal |last=Bordenave |first=G. |title=Louis Pasteur (1822–1895) |journal=Microbes Infect. |volume=5 |issue=6 |pages=553–560 |year=2003 |pmid=12758285 |doi=10.1016/S1286-4579(03)00075-3}}</ref>

[[File:Robert Koch.jpg|thumb|upright=0.8|[[Robert Koch]] showed that microorganisms caused [[disease]].]]

In 1876, [[Robert Koch]] (1843–1910) established that microorganisms can cause disease. He found that the blood of cattle that were infected with [[anthrax]] always had large numbers of ''[[Bacillus anthracis]]''. Koch found that he could transmit anthrax from one animal to another by taking a small sample of blood from the infected animal and injecting it into a healthy one, and this caused the healthy animal to become sick. He also found that he could grow the bacteria in a nutrient broth, then inject it into a healthy animal, and cause illness. Based on these experiments, he devised criteria for establishing a causal link between a microorganism and a disease and these are now known as [[Koch's postulates]].<ref>[http://nobelprize.org/nobel_prizes/medicine/laureates/1905/ The Nobel Prize in Physiology or Medicine 1905] Nobelprize.org Accessed 22 November 2006.</ref> Although these postulates cannot be applied in all cases, they do retain historical importance to the development of scientific thought and are still being used today.<ref>{{Cite journal |last=O'Brien |first=S. |last2=Goedert |first2=J. | title=HIV causes AIDS: Koch's postulates fulfilled | journal=Curr Opin Immunol | volume=8 | issue=5 | pages=613–618 | year=1996 | pmid=8902385 | doi=10.1016/S0952-7915(96)80075-6}}</ref>

The discovery of microorganisms such as ''[[Euglena]]'' that did not fit into either the [[animal]] or [[plant]] kingdoms, since they were [[photosynthetic]] like plants, but [[motile]] like animals, led to the naming of a third kingdom in the 1860s. In 1860 [[John Hogg (biologist)|John Hogg]] called this the [[Protoctista]], and in 1866 [[Ernst Haeckel]] named it the [[Protista]].<ref name=Scamardella1999>{{cite journal | last=Scamardella |first=J. M. | title=Not plants or animals: a brief history of the origin of Kingdoms Protozoa, Protista and Protoctista | year=1999 | journal=International Microbiology | volume=2 | issue=4 | pages=207–221 | pmid=10943416 | url=http://www.im.microbios.org/08december99/03%20Scamardella.pdf | access-date=1 October 2017 | archive-date=14 June 2011 | archive-url=https://web.archive.org/web/20110614000656/http://www.im.microbios.org/08december99/03%20Scamardella.pdf | url-status=dead }}</ref><ref name=Rothschild1989>{{cite journal |last=Rothschild |first=L. J. |author-link=Lynn J. Rothschild |title=Protozoa, Protista, Protoctista: what's in a name? |journal=J Hist Biol |volume=22 |issue=2 |pages=277–305 |year=1989 |pmid=11542176 |doi=10.1007/BF00139515 |s2cid=32462158 |url=https://zenodo.org/record/1232387 }}</ref><ref name=Pearl2005>{{cite book |editor1-first=Eldra Pearl |editor1-last=Solomon |editor2-first=Linda R. |editor2-last=Berg |editor3-first=Diana W. |editor3-last=Martin |chapter=Kingdoms or Domains? |chapter-url=https://books.google.com/books?id=qBOPoEc-zu4C&pg=PA421 |pages=421–7 |title=Biology |publisher=Brooks/Cole Thompson Learning |year=2005 |edition=7th |isbn=978-0-534-49276-2}}</ref>

The work of Pasteur and Koch did not accurately reflect the true diversity of the microbial world because of their exclusive focus on microorganisms having direct medical relevance. It was not until the work of [[Martinus Beijerinck]] and [[Sergei Winogradsky]] in the late 19th century that the true breadth of microbiology was revealed.<ref name=Brock>{{cite book | editor-last=Madigan |editor-first=M. |editor-last2=Martinko |editor-first2=J. | title=Brock Biology of Microorganisms | edition=13th | publisher=Pearson Education | year=2006 | isbn=978-0-321-73551-5 |page=1096}}</ref> Beijerinck made two major contributions to microbiology: the discovery of [[virus]]es and the development of [[enrichment culture]] techniques.<ref>{{cite web | last=Johnson |first=J. | title=Martinus Willem Beijerinck | work=APSnet| publisher=American Phytopathological Society | url=http://apsnet.org/education/feature/TMV/intro.html | archive-url=https://web.archive.org/web/20100620173433/http://apsnet.org/education/feature/TMV/intro.html | archive-date=2010-06-20 | year=2001 |orig-year=1998 | access-date=2 May 2010}} Retrieved from Internet Archive 12 January 2014.</ref> While his work on the [[tobacco mosaic virus]] established the basic principles of virology, it was his development of enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Winogradsky was the first to develop the concept of [[chemolithotrophy]] and to thereby reveal the essential role played by microorganisms in geochemical processes.<ref>{{cite book | last=Paustian |first=T. | last2=Roberts |first2=G. | chapter=Beijerinck and Winogradsky Initiate the Field of Environmental Microbiology | title=Through the Microscope: A Look at All Things Small | at=§&nbsp;1–14 | edition=3rd | year=2009 | publisher=Textbook Consortia | chapter-url=http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=32 | access-date=3 October 2017 | archive-date=14 September 2008 | archive-url=https://web.archive.org/web/20080914000327/http://www.microbiologytext.com/index.php?module=Book&func=displayarticle&art_id=32 | url-status=dead }}</ref> He was responsible for the first isolation and description of both [[nitrifying bacteria|nitrifying]] and [[nitrogen-fixing bacteria]].<ref name=Brock /> French-Canadian microbiologist [[Félix d'Hérelle]] co-discovered [[bacteriophage]]s and was one of the earliest applied microbiologists.<ref name =Keen>{{cite journal |last=Keen |first=E. C. |title=Felix d'Herelle and Our Microbial Future |journal=Future Microbiology |volume=7 |issue=12 |pages=1337–1339 |year=2012 |pmid=23231482|doi=10.2217/fmb.12.115}}</ref>