Editing Carl Woese (section)

=== Discovery of the third domain ===
For much of the 20th century, prokaryotes were regarded as a single group of organisms and classified based on their [[biochemistry]], [[morphology (biology)|morphology]] and [[metabolism]]. In a highly influential 1962 paper, [[Roger Stanier]] and [[C. B. van Niel]] first established the division of cellular organization into [[prokaryote]]s and [[eukaryote]]s, defining prokaryotes as those organisms lacking a [[cell nucleus]].<ref name=stanier1962>{{Cite journal | doi = 10.1007/BF00425185 | last1 = Stanier | first1 = R. Y. | author-link1 = Roger Stanier| last2 = Van Niel | first2 = C. B. | author-link2 = C. B. van Niel| title = The concept of a bacterium | journal = Archiv für Mikrobiologie | volume = 42 | pages = 17–35 | year = 1962 | issue = 1 | pmid = 13916221| bibcode = 1962ArMic..42...17S | s2cid = 29859498 }}</ref><ref name=pace2009>{{Cite journal | last1 = Pace | first1 = N. R. | author-link1 = Norman R. Pace| title = Problems with "Procaryote" | doi = 10.1128/JB.01224-08 | journal = Journal of Bacteriology | volume = 191 | issue = 7 | pages = 2008–2010; discussion 2010 | year = 2009 | pmid =  19168605| pmc =2655486 }}</ref> Adapted from [[Édouard Chatton]]'s generalization, Stanier and Van Niel's concept was quickly accepted as the most important distinction among organisms; yet they were nevertheless skeptical of microbiologists' attempts to construct a natural [[phylogenetic]] classification of bacteria.<ref name=sapp2005>{{Cite journal | last1 = Sapp | first1 = J. | author-link1 = Jan Sapp| title = The Prokaryote-Eukaryote Dichotomy: Meanings and Mythology | doi = 10.1128/MMBR.69.2.292-305.2005 | journal = Microbiology and Molecular Biology Reviews | volume = 69 | issue = 2 | pages = 292–305 | year = 2005 | pmid =  15944457| pmc =1197417 }}</ref> However, it became generally assumed that all life shared a common prokaryotic (implied by the [[Greek language|Greek]] root πρό (pro-), before, in front of) ancestor.<ref name="pace2009" /><ref name=oren2010>{{Cite book| chapter = Concepts About Phylogeny of Microorganisms–an Historical Perspective| publisher = Caister Academic Press| isbn = 9781904455677| pages = 1–22|editor1=Aharon Oren |editor2=R. Thane Papke 
| last = Oren| first = Aharon| title = Molecular Phylogeny of Microorganisms| location = Norfolk, UK| date = 2010-07-01| chapter-url = https://books.google.com/books?id=a5t9DYZ-wccC&q=concepts+Aharon+Oren+phylogeny&pg=PR7}}</ref>

In 1977, Woese and [[George E. Fox]] experimentally disproved this universally held hypothesis about the basic structure of the [[tree of life (biology)|tree of life]].<ref name="pace2011pnas" /> Woese and Fox discovered a kind of microbial life which they called the “archaebacteria” ([[Archaea]]).<ref name="woese1977" /> They reported that the archaebacteria comprised "a third kingdom" of life as distinct from bacteria as plants and animals.<ref name="woese1977" /> Having defined Archaea as a new "urkingdom" (later [[domain (biology)|domain]]) which were neither bacteria nor eukaryotes, Woese redrew the [[Taxonomy (biology)|taxonomic]] tree. His [[three-domain system]], based on phylogenetic relationships rather than obvious morphological similarities, divided life into 23 main divisions, incorporated within three domains: [[Bacteria]], [[Archaea]], and [[Eukaryote|Eucarya]].<ref name="Woese_1990" />

[[File:PhylogeneticTree, Woese 1990.PNG|thumb|left|450px|Phylogenetic tree based on Woese et al. rRNA analysis. The vertical line at bottom represents the [[last universal common ancestor]] (LUCA).<ref name="Woese_1990"/>]]

Acceptance of the validity of Woese's phylogenetically valid classification was a slow process. Prominent biologists including [[Salvador Luria]] and [[Ernst Mayr]] objected to his division of the prokaryotes.<ref>{{Cite journal | title = Two empires or three?| doi = 10.1073/pnas.95.17.9720| volume = 95
| issue = 17| pages = 9720–9723| last = Mayr| first = Ernst| author-link = Ernst Mayr| journal = Proceedings of the National Academy of Sciences |year = 1998| bibcode=1998PNAS...95.9720M| pmid=9707542| pmc=33883| doi-access = free}}</ref><ref name="sapp2007">{{Cite journal| title = The structure of microbial evolutionary theory| doi = 10.1016/j.shpsc.2007.09.011| pmid = 18053933|  volume = 38| issue = 4| pages = 780–95 | last = Sapp| first = Jan A.| author-link = Jan Sapp| journal = Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences |date=December 2007}}</ref> Not all criticism of him was restricted to the scientific level. A decade of labor-intensive [[oligonucleotide]] cataloging left him with a reputation as "a crank," and Woese would go on to be dubbed as "Microbiology's Scarred Revolutionary" by a news article printed in the journal ''[[science (journal)|Science]]''.<ref name="morell1997">{{Cite journal| title = Microbiology's scarred revolutionary| doi = 10.1126/science.276.5313.699| issn = 0036-8075| volume = 276| issue = 5313| pages = 699–702| last = Morell| first = V.| journal = Science| date = 1997-05-02| pmid = 9157549| s2cid = 84866217}}</ref> The growing body of supporting data led the [[scientific community]] to accept the Archaea by the mid-1980s.<ref name="sapp2009"/> Today, few scientists cling to the idea of a unified Prokarya.

Woese's work on Archaea is also significant in its implications for the search for life on other planets. Before the discovery by Woese and Fox, scientists thought that Archaea were extreme organisms that evolved from the microorganisms more familiar to us. Now, most believe they are ancient, and may have robust evolutionary connections to the first organisms on Earth.<ref>{{Cite journal| title = Archaeal phylogenomics provides evidence in support of a methanogenic origin of the Archaea and a thaumarchaeal origin for the eukaryotes| doi = 10.1098/rspb.2010.1427| volume = 278| issue = 1708| pages = 1009–1018| last = Kelly| first = S.|author2=B. Wickstead |author3=K. Gull | journal = Proceedings of the Royal Society B: Biological Sciences| date = 2010-09-29 | pmid=20880885 | pmc=3049024}}</ref> Organisms similar to those archaea that exist in extreme environments may have developed on other planets, some of which harbor conditions conducive to [[extremophile]] life.<ref name="stetter2006">{{Cite journal| title = Hyperthermophiles in the history of life| doi = 10.1098/rstb.2006.1907| volume = 361| issue = 1474| pages = 1837–1843| last = Stetter| first = Karl O. | journal = Philosophical Transactions of the Royal Society B: Biological Sciences| date = 2006-10-29| pmc = 1664684| pmid=17008222}}</ref>

Notably, Woese's elucidation of the [[Tree of life (biology)|tree of life]] shows the overwhelming diversity of microbial lineages: single-celled organisms represent the vast majority of the biosphere's genetic, metabolic, and ecologic niche diversity.<ref name=woese2006prok>{{Cite book | last1 = Woese | first1 = C. R. | chapter = How We Do, Don’t and Should Look at Bacteria and Bacteriology | title = The Prokaryotes | pages = 3–4 | year = 2006 | isbn = 978-0-387-25476-0 | doi = 10.1007/0-387-30741-9_1}}</ref> As microbes are crucial for many [[biogeochemical cycle]]s and to the continued function of the biosphere, Woese's efforts to clarify the evolution and diversity of microbes provided an invaluable service to [[ecologists]] and [[conservationists]]. It was a major contribution to the theory of [[evolution]] and to our knowledge of the history of life.<ref name=pnas2012>{{cite journal | doi = 10.1073/pnas.1120749109 | issn = 1091-6490 | volume = 109 | issue = 4 | pages = 1019–1021 | last = Nair | first = Prashant | title = Woese and Fox: Life, rearranged | journal = Proceedings of the National Academy of Sciences | date = 2012-01-17 | bibcode=  2012PNAS..109.1019N | pmid=22308527 | pmc=3268309| doi-access = free }}</ref>

Woese wrote, "My evolutionary concerns center on the bacteria and the archaea, whose evolutions cover most of the planet's 4.5-billion-year history. Using ribosomal RNA sequence as an evolutionary measure, my laboratory has reconstructed the phylogeny of both groups, and thereby provided a phylogenetically valid system of classification for prokaryotes. The discovery of the archaea was in fact a product of these studies".<ref name=mcb />