Editing Microorganism (section)

===Evolution===
{{further|Timeline of the evolutionary history of life|Earliest known life forms}}
{{PhylomapB||caption=[[Carl Woese]]'s 1990 [[phylogenetic tree]] based on [[rRNA]] data shows the domains of [[Bacteria]], [[Archaea]], and [[Eukaryota]]. All are microorganisms except some eukaryote groups.|size=325px}}
Single-celled microorganisms were the [[Origin of life|first forms of life]] to develop on Earth, approximately 3.5 billion years ago.<ref>{{Cite journal |author=Schopf, J. |title=Fossil evidence of Archaean life |journal=Philos Trans R Soc Lond B Biol Sci |volume=361 |issue=1470 |pages=869–885 |year=2006 |pmid=16754604 |doi=10.1098/rstb.2006.1834 |pmc=1578735}}</ref><ref>{{Cite journal |last=Altermann |first=W. |last2=Kazmierczak |first2=J. |title=Archean microfossils: a reappraisal of early life on Earth |journal=Res Microbiol |volume=154 |issue=9 |pages=611–617 |year=2003 |pmid=14596897 | doi=10.1016/j.resmic.2003.08.006|doi-access=free }}</ref><ref>{{Cite journal|last=Cavalier-Smith |first=T. |author-link=Thomas Cavalier-Smith |title=Cell evolution and Earth history: stasis and revolution  |journal=Philos Trans R Soc Lond B Biol Sci |volume=361 |issue=1470 |pages=969–1006 |year=2006 |pmid=16754610 |doi=10.1098/rstb.2006.1842 |pmc=1578732}}</ref> Further evolution was slow,<ref>{{Cite journal| last=Schopf |first=J. | title=Disparate rates, differing fates: tempo and mode of evolution changed from the Precambrian to the Phanerozoic | pmc=44277| journal=PNAS | volume=91 | issue=15 | pages=6735–6742 | year=1994 | pmid=8041691 | doi=10.1073/pnas.91.15.6735 | bibcode=1994PNAS...91.6735S| doi-access=free }}</ref> and for about 3&nbsp;billion years in the [[Precambrian]] [[Eon (geology)|eon]], (much of the history of [[life|life on Earth]]), all [[organism]]s were microorganisms.<ref>{{Cite journal|author=Stanley, S. |title=An Ecological Theory for the Sudden Origin of Multicellular Life in the Late Precambrian |journal=PNAS |volume=70 |issue=5 |pages=1486–1489 |date=May 1973 |pmid=16592084 |pmc=433525 | doi=10.1073/pnas.70.5.1486 |bibcode=1973PNAS...70.1486S |doi-access=free }}</ref><ref>{{Cite journal |author1=DeLong, E. |author2=Pace, N. | title=Environmental diversity of bacteria and archaea | journal=Syst Biol | volume=50 | issue=4 | pages=470–478 | year=2001 |pmid=12116647 | doi=10.1080/106351501750435040|citeseerx=10.1.1.321.8828 }}</ref> Bacteria, algae and fungi have been identified in [[amber]] that is 220&nbsp;million years old, which shows that the [[Morphology (biology)|morphology]] of microorganisms has changed little since at least the [[Triassic]] period.<ref>{{Cite journal |author=Schmidt, A. |author2=Ragazzi, E. |author3=Coppellotti, O. |author4=Roghi, G. | title=A microworld in Triassic amber | journal=Nature | volume=444 | issue=7121 | page=835 | year=2006 | pmid=17167469 | doi=10.1038/444835a |bibcode=2006Natur.444..835S |s2cid=4401723 | doi-access=free }}</ref> The newly discovered [[Nickel#Biological role|biological role played by nickel]], however – especially that brought about by [[Types of volcanic eruption|volcanic eruptions]] from the [[Siberian Traps]] – may have accelerated the evolution of [[methanogen]]s towards the end of the [[Permian–Triassic extinction event]].<ref>{{cite web |url= http://www.space.com/26654-microbe-innovation-started-largest-earth-extinction.html |title= Microbe's Innovation May Have Started Largest Extinction Event on Earth |last= Schirber |first=Michael |date= 27 July 2014 |publisher=Astrobiology Magazine |website= Space.com |quote=That spike in nickel allowed methanogens to take off.}}</ref>

Microorganisms tend to have a relatively fast rate of evolution. Most microorganisms can reproduce rapidly, and bacteria are also able to freely exchange genes through [[Bacterial conjugation|conjugation]], [[Transformation (genetics)|transformation]] and [[Transduction (genetics)|transduction]], even between widely divergent species.<ref>{{Cite journal| author=Wolska, K. | title=Horizontal DNA transfer between bacteria in the environment | journal=Acta Microbiol Pol | volume=52 | issue=3 | pages=233–243 | year=2003 |pmid=14743976}}</ref> This [[horizontal gene transfer]], coupled with a high [[mutation]] rate and other means of transformation, allows microorganisms to swiftly [[biological evolution|evolve]] (via [[natural selection]]) to survive in new environments and respond to [[stressors|environmental stresses]]. This rapid evolution is important in medicine, as it has led to the development of [[multidrug resistance|multidrug resistant]] [[pathogenic bacteria]], ''superbugs'', that are [[antimicrobial resistance|resistant to antibiotics]].<ref>{{Cite journal |author=Enright, M. |author2=Robinson, D. |author3=Randle, G. |author4=Feil, E. |author5=Grundmann, H. |author6=Spratt, B. | title=The evolutionary history of methicillin-resistant ''Staphylococcus aureus'' (MRSA) | journal=Proc Natl Acad Sci USA | volume=99 | issue=11 | pages=7687–7692 |date=May 2002 | pmid=12032344 |pmc=124322 | doi=10.1073/pnas.122108599|bibcode=2002PNAS...99.7687E |doi-access=free }}</ref>

A possible transitional form of microorganism between a prokaryote and a eukaryote was discovered in 2012 by Japanese scientists. ''[[Parakaryon myojinensis]]'' is a unique microorganism larger than a typical prokaryote, but with nuclear material enclosed in a membrane as in a eukaryote, and the presence of endosymbionts. This is seen to be the first plausible evolutionary form of microorganism, showing a stage of development from the prokaryote to the eukaryote.<ref name="Parakaryon">{{cite web |title=Deep sea microorganisms and the origin of the eukaryotic cell |url=http://protistology.jp/journal/jjp47/JJP47YAMAGUCHI.pdf |access-date=24 October 2017}}</ref><ref name="Yamaguchi">{{cite journal|last1=Yamaguchi |display-authors=et al|first1=Masashi |title=Prokaryote or eukaryote? A unique microorganism from the deep sea |issue=6 |journal=Journal of Electron Microscopy |volume=61 |pages=423–431 |doi=10.1093/jmicro/dfs062 |pmid=23024290 |date=1 December 2012}}</ref>