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Os '''crenarqueotas''' ou '''Crenarchaeota''' (tamén chamados '''Crenarchaea''', '''eocitos''' ou '''Eocyta''') son [[procariota]]s que forman un [[filo]] (ou [[reino (bioloxía)|reino]]) do [[dominio (bioloxía)|dominio]] [[Archaea]]. <ref>Ver [[National Center for Biotechnology Information|NCBI]] [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=28889 webpage on Crenarchaeota]</ref><ref>C.Michael Hogan. 2010. [http://www.eoearth.org/article/Archaea?topic=49496 ''Archaea''. eds. E.Monosson & C.Cleveland, Encyclopedia of Earth. National Council for Science and the Environment, Washington DC.]</ref><ref>Datos tomados de {{cite web | url=ftp://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=[[National Center for Biotechnology Information]] | accessdate=2007-03-19}}</ref> <ref>[http://www.tolweb.org/Crenarchaeota/9 Tree of Life]: Crenarchaeota</ref> Inicialmente, os Crenarchaeota pensábase que eran [[extremófilo|extremófilas]] (como os organismos [[termófilo]]s e [[psicrófilo]]s) pero estudos recentes identificáronas como as arqueas máis abundantes no medio mariño. <ref name=Brock>{{Cita libro | author = Madigan M; Martinko J (editors). | title = Brock Biology of Microorganisms | edition = 11th | publisher = Prentice Hall | year = 2005 | isbn = 0-13-144329-1}}</ref> Orixinalmente, foron separadas das outras arqueas baseándose nas secuencias do seu [[ARNr]]; porén, outras características fisiolóxicos, como a falta de [[histona]]s apoiaban esta separación, aínda que se atopou que algunhas especies de crenarqueotas tiñan histonas. <ref name=Cubonova2005>{{citeCita journalpublicación periódica | author=Cubonova L, Sandman K, Hallam SJ, Delong EF, Reeve JN | title=Histones in Crenarchaea | journal=Journal of Bacteriology | year=2005 | pages=5482–5485 | volume=187 | issue=15 | pmid=16030242 | doi=10.1128/JB.187.15.5482-5485.2005 | pmc=1196040}}</ref> Ata hai pouco todas as Crenarchaea cultivadas foran organismos termófilos ou [[hipertermófilo]]s, algúns dos cales podían crecer a temperaturas de ata 113 °C. <ref name=Blochl_1997>{{citeCita journalpublicación periódica | author=Blochl E, Rachel R, Burggraf S, Hafenbradl D, Jannasch HW, Stetter KO | title=''Pyrolobus fumarii'', gen. and sp. nov., represents a novel group of archaea, extending the upper temperature limit for life to 113 °C | journal=Extremophiles | year=1997 | pages=14–21 | volume=1 | issue=1 | pmid=9680332 | doi=10.1007/s007920050010 }}</ref> Estes organismos son [[Gram-negativa|Gram-negativos]] e son morfoloxicamente moi variados, e poden ter forma de [[bacilo]], [[coco (bacteria)|coco]], filamentosa ou poden ser células con formas estrañas. <ref name=Bergeys_2001>{{Cita libro | author = Garrity GM, Boone DR (editors) | title = [[Bergey's Manual of Systematic Bacteriology]] Volume 1: The Archaea and the Deeply Branching and Phototrophic Bacteria | edition = 2nd | publisher = Springer | year = 2001 | isbn = 0-387-98771-1}}</ref>
== Termófilos ==
Os tipos de metabolismo que presentan son diversos, desde [[heterótrofo|quimioorganótrofos]] a [[autótrofo|quimiolitótrofos]]. Os quimiolitótrofos [[aerobio]]s obteñen enerxía da oxidación de varios compostos sulfúricos, hidróxeno ou ferro ferroso, entanto que os quimiolitótrofos [[anaerobio]]s reducen [[xofre]], [[tiosulfato]] ou producen [[nitrato]]s, [[sulfuro de hidróxeno]] ou [[amoníaco]]. Os quimioorganótrofos crecen sobre substratos orgánicos complexos, azucres, aminoácidos ou polímeros. Varias especies son produtores primarios e usan o [[dióxido de carbono]] como [[fixación do carbono|fonte única de carbono]], obtendo enerxía da oxidación de substancias inorgánicas tales como xofre ou hidróxeno, ou pola redución de xofre ou nitrato.
Un dos membros de Crenarchaeota mellor coñecidos é ''Sulfolobus solfataricus''. Este organismo foi orixinalmente illado de mananciais xeotermais sulfurosos de [[Italia]], e crece a 80 °C e a [[pH]] entre 2 e 4. <ref name=Zillig_1980>{{citeCita journalpublicación periódica | author = Zillig W, Stetter KO, Wunderl S, Schulz W, Priess H, Scholz I| title = The Sulfolobus-"Caldariellard" group: Taxonomy on the basis of the structure of DNA-dependent RNA polymerases | journal = Arch. Microbiol. | year = 1980 | volume = 125 | issue = 3| pages = 259–269 | url= | doi = 10.1007/BF00446886}}</ref> Despois da súa caracterización inicial, foron atopadas outras especies termófilas do mesmo xénero por todo o mundo. A diferenza da gran maioría dos termófilos cultivados, ''[[Sulfolobus]]'' crece en condicións [[aeróbico|aeróbicas]] e é [[quimioorganótrofo]] (obtén a súa enerxía de fontes orgánicas como azucres). Estes factores permiten cultivalas máis facilmente no laboratorio ca os [[organismo anaeróbico|organismos anaeróbicos]], o que fixo de ''Sulfolobus'' un [[organismo modelo]] para o estudo dos hipertermófilos e dos virus que se replican dentro deles.
== Mesófilos, psicrófilos e especies mariñas ==
[[Ficheiro:Eocyte hypothesis gl.png|400px|miniatura|dereita|[[Hipótese do eocito]].<ref>{{citeCita journalpublicación periódica | author = Cox, C. J., Foster, P. G., Hirt, R. P., Harris, S. R., Embley, T. M. | year = 2008 | title = The archaebacterial origin of eukaryotes | journal = Proc Natl Acad Sci USA | volume = 105 | issue = 51 | pages = 20356–61 | doi = 10.1073/pnas.0810647105 | pmid = 19073919 | pmc = 2629343|bibcode = 2008PNAS..10520356C }}</ref>]]
A partir de 1992, publicáronse datos sobre as secuencias de xenes que pertencían a Crenarchaeota dos ambientes mariños <ref name=Fuhrman_1992>{{citeCita journalpublicación periódica | author=Fuhrman JA, McCallum K, Davis AA | title=Novel major archaebacterial group from marine plankton | journal=Nature | year=1992 | pages=148–9 | volume=356 | issue=6365 | pmid=1545865 | doi=10.1038/356148a0 |bibcode = 1992Natur.356..148F }}</ref><sup>,</sup><ref name=DeLong_1992>{{citeCita journalpublicación periódica | author=DeLong EF | title=Archaea in coastal marine environments | journal=Proc Natl Acad Sci USA | year=1992 | pages=5685–9 | volume=89 | issue=12 | pmid=1608980 | doi=10.1073/pnas.89.12.5685 | pmc=49357|bibcode = 1992PNAS...89.5685D }}</ref> e outros. Desde entón utilizáronse tamén análises dos abundantes lípidos de membrana específicos das Crenarchaea tomados do océano para determinar a concentración destas “crenarqueotas de baixa temperatura” (usando o paleotermómetro [[TEX-86]]).
Estas análises ambientais recentes baseados en xenes, secuencias de [[ARNr]] e lípidos indican que as Crenarchaeota tamén se distribúen extensamente en ambientes de baixa temperatura tales como solos, sedimentos, auga doce e océanos. <ref name=DeLong_1992>{{Cita publicación| autor=DeLong EF | título=Archaea in coastal marine environments | revista=Proc Natl Acad Sci U S A |ano=1992 |páxinas=5685-9 |volume=89 | número=12 | id=PMID 1608980 [http://www.pnas.org/cgi/content/abstract/89/12/5685 fulltext] }}</ref><sup>,</sup><ref name=Fuhrman_1993>{{Cita publicación| autor=Fuhrman JA, McCallum K, Davis AA | título=Phylogenetic diversity of subsurface marine microbial communities from the Atlantic and Pacific Oceans | revista=Appl Environ Microbiol |ano=1993 |páxinas=1294-302 |volume=59 | número=5 | id= PMID 7685997 }}</ref> Aínda que ningún destes organismos puido ser cultivado, o ambiente de obtención, xunto cos datos xenómicos, fai supoñer que son organismos [[Mesófilo (organismo)|mesófilos]] ou [[psicrófilo]]s. Este extenso grupo de arqueas parece derivar de antepasados termofílicos que invadiron diversos hábitats de baixa temperatura.
==== Revistas científicas ====
* {{citeCita journalpublicación periódica | last = Cavalier-Smith | first = T | year = 2002 | title = The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification | journal = Int. J. Syst. Evol. Microbiol. | volume = 52 | pages = 7–76 | pmid = 11837318 | issue = Pt 1}}
* {{citeCita journalpublicación periódica | last = Stackebrandt | first = E | coauthors = Frederiksen W, Garrity GM, Grimont PA, Kampfer P, Maiden MC, Nesme X, Rossello-Mora R, Swings J, Truper HG, Vauterin L, Ward AC, Whitman WB | year = 2002 | title = Report of the ad hoc committee for the re-evaluation of the species definition in bacteriology | journal = Int. J. Syst. Evol. Microbiol. | volume = 52 | pages = 1043–1047 | pmid = 12054223 | doi = 10.1099/ijs.0.02360-0 | issue = Pt 3}}
* {{citeCita journalpublicación periódica | last = Gurtler | first = V | coauthors = Mayall BC | year = 2001 | title = Genomic approaches to typing, taxonomy and evolution of bacterial isolates | journal = Int. J. Syst. Evol. Microbiol. | volume = 51 | pages = 3–16 | pmid = 11211268 | issue = Pt 1}}
* {{citeCita journalpublicación periódica | last = Dalevi | first = D | coauthors = Hugenholtz P, Blackall LL | year = 2001 | title = A multiple-outgroup approach to resolving division-level phylogenetic relationships using 16S rDNA data | journal = Int. J. Syst. Evol. Microbiol. | volume = 51 | pages = 385–391 | pmid = 11321083 | issue = Pt 2}}
* {{citeCita journalpublicación periódica | last = Keswani | first = J | coauthors = Whitman WB | year = 2001 | title = Relationship of 16S rRNA sequence similarity to DNA hybridization in prokaryotes | journal = Int. J. Syst. Evol. Microbiol. | volume = 51 | pages = 667–678 | pmid = 11321113 | issue = Pt 2}}
* {{citeCita journalpublicación periódica | last = Young | first = JM | year = 2001 | title = Implications of alternative classifications and horizontal gene transfer for bacterial taxonomy | journal = Int. J. Syst. Evol. Microbiol. | volume = 51 | pages = 945–953 | pmid = 11411719 | issue = Pt 3 | doi=10.1099/00207713-51-3-945}}
* {{citeCita journalpublicación periódica | last = Christensen | first = H | coauthors = Bisgaard M, Frederiksen W, Mutters R, Kuhnert P, Olsen JE | year = 2001 | title = Is characterization of a single isolate sufficient for valid publication of a new genus or species? Proposal to modify recommendation 30b of the Bacteriological Code (1990 Revision) | journal = Int. J. Syst. Evol. Microbiol. | volume = 51 | pages = 2221–2225 | pmid = 11760965 | issue = Pt 6 | doi=10.1099/00207713-51-6-2221}}
* {{citeCita journalpublicación periódica | last = Christensen | first = H | coauthors = Angen O, Mutters R, Olsen JE, Bisgaard M | year = 2000 | title = DNA-DNA hybridization determined in micro-wells using covalent attachment of DNA | journal = Int. J. Syst. Evol. Microbiol. | volume = 50 | pages = 1095–1102 | pmid = 10843050 | doi=10.1099/00207713-50-3-1095 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Xu | first = HX | coauthors = Kawamura Y, Li N, Zhao L, Li TM, Li ZY, Shu S, Ezaki T | year = 2000 | title = A rapid method for determining the G+C content of bacterial chromosomes by monitoring fluorescence intensity during DNA denaturation in a capillary tube | journal = Int. J. Syst.Evol. Microbiol. | volume = 50 | pages = 1463–1469 | pmid = 10939651 | doi=10.1099/00207713-50-4-1463 | issue = 4}}
* {{citeCita journalpublicación periódica | last = Young | first = JM | year = 2000 | title = Suggestions for avoiding on-going confusion from the Bacteriological Code | journal = Int. J. Syst. Evol. Microbiol. | volume = 50 | pages = 1687–1689 | pmid = 10939677 | doi=10.1099/00207713-50-4-1687 | issue = 4}}
* {{citeCita journalpublicación periódica | last = Hansmann | first = S | coauthors = Martin W | year = 2000 | title = Phylogeny of 33 ribosomal and six other proteins encoded in an ancient gene cluster that is conserved across prokaryotic genomes: influence of excluding poorly alignable sites from analysis | journal = Int. J. Syst. Evol. Microbiol. | volume = 50 | pages = 1655–1663 | pmid = 10939673 | doi=10.1099/00207713-50-4-1655 | issue = 4}}
* {{citeCita journalpublicación periódica | last = Tindall | first = BJ | year = 1999 | title = Proposal to change the Rule governing the designation of type strains deposited under culture collection numbers allocated for patent purposes | journal = Int. J. Syst. Bacteriol. | volume = 49 | pages = 1317–1319 | pmid = 10490293 | doi = 10.1099/00207713-49-3-1317 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Tindall | first = BJ | year = 1999 | title = Proposal to change Rule 18a, Rule 18f and Rule 30 to limit the retroactive consequences of changes accepted by the ICSB | journal = Int. J. Syst. Bacteriol. | volume = 49 | pages = 1321–1322 | pmid = 10425797 | doi = 10.1099/00207713-49-3-1321 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Tindall | first = BJ | year = 1999 | title = Misunderstanding the Bacteriological Code | journal = Int. J. Syst. Bacteriol. | volume = 49 | pages = 1313–1316 | pmid = 10425796 | doi = 10.1099/00207713-49-3-1313 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Tindall | first = BJ | year = 1999 | title = Proposals to update and make changes to the Bacteriological Code | journal = Int. J. Syst. Bacteriol. | volume = 49 | pages = 1309–1312 | pmid = 10425795 | doi = 10.1099/00207713-49-3-1309 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Burggraf | first = S | coauthors = Huber H, Stetter KO | year = 1997 | title = Reclassification of the crenarchael orders and families in accordance with 16S rRNA sequence data | journal = Int. J. Syst. Bacteriol. | volume = 47 | pages = 657–660 | pmid = 9226896 | doi = 10.1099/00207713-47-3-657 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Palys | first = T | coauthors = Nakamura LK, Cohan FM | year = 1997 | title = Discovery and classification of ecological diversity in the bacterial world: the role of DNA sequence data | journal = Int. J. Syst. Bacteriol. | volume = 47 | pages = 1145–1156 | pmid = 9336922 | doi = 10.1099/00207713-47-4-1145 | issue = 4}}
* {{citeCita journalpublicación periódica | last = Euzeby | first = JP | year = 1997 | title = List of Bacterial Names with Standing in Nomenclature: a folder available on the Internet | journal = Int. J. Syst. Bacteriol. | volume = 47 | pages = 590–592 | pmid = 9103655 | doi = 10.1099/00207713-47-2-590 | issue = 2}}
* {{citeCita journalpublicación periódica | last = Clayton | first = RA | coauthors = Sutton G, Hinkle PS Jr, Bult C, Fields C | year = 1995 | title = Intraspecific variation in small-subunit rRNA sequences in GenBank: why single sequences may not adequately represent prokaryotic taxa | journal = Int. J. Syst. Bacteriol. | volume = 45 | pages = 595–599 | pmid = 8590690 | doi = 10.1099/00207713-45-3-595 | issue = 3}}
* {{citeCita journalpublicación periódica | last = Murray | first = RG | coauthors = Schleifer KH | year = 1994 | title = Taxonomic notes: a proposal for recording the properties of putative taxa of procaryotes | journal = Int. J. Syst. Bacteriol. | volume = 44 | pages = 174–176 | pmid = 8123559 | doi = 10.1099/00207713-44-1-174 | issue = 1}}
* {{citeCita journalpublicación periódica | last = Winker | first = S | coauthors = Woese CR | year = 1991 | title = A definition of the domains Archaea, Bacteria and Eucarya in terms of small subunit ribosomal RNA characteristics | journal = Syst. Appl. Microbiol. | volume = 14 | pages = 305–310 | pmid = 11540071 | issue = 4}}
* {{citeCita journalpublicación periódica | last = Woese | first = CR | coauthors = Kandler O, Wheelis ML | year = 1990 | title = Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya | journal = Proc. Natl. Acad. Sci. USA | volume = 87 | pages = 4576–4579 | pmid = 2112744 | doi = 10.1073/pnas.87.12.4576 | issue = 12 | pmc = 54159 | bibcode=1990PNAS...87.4576W}}
* {{citeCita journalpublicación periódica | last = Achenbach-Richter | first = L | coauthors = Woese CR | year = 1988 | title = The ribosomal gene spacer region in archaebacteria | journal = Syst. Appl. Microbiol. | volume = 10 | pages = 211–214 | pmid = 11542149}}
* {{citeCita journalpublicación periódica | last = McGill | first = TJ | coauthors = Jurka J, Sobieski JM, Pickett MH, Woese CR, Fox GE | year = 1986 | title = Characteristic archaebacterial 16S rRNA oligonucleotides | journal = Syst. Appl. Microbiol. | volume = 7 | pages = 194–197 | pmid = 11542064 | doi = 10.1016/S0723-2020(86)80005-4 | issue = 2–3}}
* {{citeCita journalpublicación periódica | last = Woese | first = CR | coauthors = Gupta R, Hahn CM, Zillig W, Tu J | year = 1984 | title = The phylogenetic relationships of three sulfur dependent archaebacteria | journal = Syst. Appl. Microbiol. | volume = 5 | pages = 97–105 | pmid = 11541975 | doi = 10.1016/S0723-2020(84)80054-5}}
* {{citeCita journalpublicación periódica | last = Woese | first = CR | coauthors = Olsen GJ | year = 1984 | title = The phylogenetic relationships of three sulfur dependent archaebacteria | journal = Syst. Appl. Microbiol. | volume = 5 | pages = 97–105 | pmid = 11541975 | doi=10.1016/S0723-2020(84)80054-5}}
* {{citeCita journalpublicación periódica | last = Woese | first = CR | coauthors = Fox GE | year = 1977 | title = Phylogenetic structure of the prokaryotic domain: the primary kingdoms | journal = Proc. Natl. Acad. Sci. USA | volume = 74 | pages = 5088–5090 | pmid = 270744 | doi = 10.1073/pnas.74.11.5088 | issue = 11 | pmc = 432104|bibcode = 1977PNAS...74.5088W }}
==== Libros ====
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