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| Archaea (Archaebacteria)|
Temporal range: 3.5-0Ga
| Halobacterium sp. strain NRC-1,|
each cell about 5 μm long
|Kingdoms and phyla|
Archaea are tiny, simple organisms. They were originally discovered in extreme environments (extremophiles), but are now thought to be common to more average conditions. Many can survive at very high (over 80 °C) or very low temperatures, or highly salty, acidic or alkaline water. Some have been found in geysers, black smokers, oil wells, and hot vents in the deep ocean. Recent research has found ammonia-eating archaea in soil and seawater.
In the past they had been classed with bacteria as prokaryotes (or Kingdom Monera) and named archaebacteria, but this is a mistake. The Archaea have an independent evolutionary history and show many differences in their biochemistry from other forms of life. They are now classified as a separate domain in the three-domain system. In this system, the three distinct branches of evolutionary descent are the Archaea, Bacteria and Eukaryota.
Comparison to other domains
The following table compares some major characteristics of the three domains, to illustrate their similarities and differences. Many of these characteristics are also discussed below.
|Cell membrane||Ether-linked lipids, pseudopeptidoglycan||Ester-linked lipids, peptidoglycan||Ester-linked lipids, various structures|
|Gene structure||Circular chromosomes, similar translation and transcription to Eukarya||Circular chromosomes, unique translation and transcription||Multiple, linear chromosomes, similar translation and transcription to Archaea|
|Internal cell structure||No membrane-bound organelles (but questioned:) or nucleus||No membrane-bound organelles or nucleus||Membrane-bound organelles and nucleus|
|Metabolism||Various, with methanogenesis unique to Archaea||Various, including photosynthesis, aerobic and anaerobic respiration, fermentation, and autotrophy||Photosynthesis, cellular respiration and fermentation|
|Reproduction||Asexual reproduction, horizontal gene transfer||Asexual reproduction, horizontal gene transfer||Sexual and asexual reproduction|
- No archaean species can do photosynthesis.
- Archaea only reproduce asexually.
- Archaea show high levels of horizontal gene transfer between lineages.
- Many archaea live in extreme environments.
- Unlike bacteria, no archaea produce spores.
- Archaea are common in the ocean, and especially in the plankton. They make up to 20% of all microbial cells in the ocean.p475
- Carl Woese discovered the Archaea in 1978.
- Barry E.R. & Bell S.D. 2006. DNA replication in the Archaea. Microbiology and molecular biology reviews (MMBR) '70, 876-887.
- Kelman L.M. & Kelman Z. 2003. Archaea: An archetype for replication initiation studies? Molecular microbiology, 48, 605-615.
- Archaea -Citizendium
- "Taxa above the rank of class". List of Prokaryotic names with Standing in Nomenclature. http://www.bacterio.net/-aboveclass.html.
- Cavalier-Smith, T. (2014). "The neomuran revolution and phagotrophic origin of eukaryotes and cilia in the light of intracellular coevolution and a revised tree of life". Cold Spring Harb. Perspect. Biol. 6 (9). PMID 25183828..
- "Rooting the domain archaea by phylogenomic analysis supports the foundation of the new kingdom Proteoarchaeota". Genome Biology and Evolution 7 (1): 191–204. December 2014. . . .
- NCBI taxonomy page on Archaea. https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&id=2157&lvl=5&lin=f&keep=1&srchmode=1&unlock.
- Pace NR (May 2006). "Time for a change". Nature 441 (7091): 289. . .
- Information is from Willey JM, Sherwood LM, Woolverton CJ. Microbiology 7th ed. (2008), Ch. 19 pp. 474–475, except where noted.
- Thomas Heimerl (13 June 2017). "A Complex endomembrane system in the Archaeon Ignicoccus hospitalis tapped by Nanoarchaeum equitans". Frontiers in Microbiology. .
- Jurtshuk, Peter (1996). Medical Microbiology (4th ed.). Galveston (TX): University of Texas Medical Branch at Galveston. https://www.ncbi.nlm.nih.gov/books/NBK7919/. Retrieved 5 November 2014.
- Howland, John L. (2000). The surprising Archaea: discovering another domain of life. Oxford: Oxford University Press. .
- Garrett RA, Klenk H (2005). Archaea: evolution, physiology and molecular biology. WileyBlackwell. .
- Schaechter, M (2009). Archaea (overview) in The desk encyclopedia of microbiology, 2nd edition. San Diego and London: Elsevier Academic Press. .
- Schäfer G. et al 1999. Bioenergetics of the Archaea. Microbiol. Mol. Biol. Rev. 63 (3): 570–620. PMID 10477309.
- de Queiroz K (2005). "Ernst Mayr and the modern concept of species". Proc. Natl. Acad. Sci. U.S.A. 102 (Suppl 1): 6600–7. . . . http://www.pnas.org/cgi/pmidlookup?view=long&pmid=15851674.
- Eppley JM, Tyson GW, Getz WM, Banfield JF (2007). "Genetic exchange across a species boundary in the archaeal genus ferroplasma". Genetics 177 (1): 407–16. . . . http://www.genetics.org/cgi/pmidlookup?view=long&pmid=17603112.
- Papke RT, Zhaxybayeva O, Feil EJ, Sommerfeld K, Muise D, Doolittle WF (2007). "Searching for species in haloarchaea". Proc. Natl. Acad. Sci. U.S.A. 104 (35): 14092–7. . . . http://www.pnas.org/cgi/pmidlookup?view=long&pmid=17715057.
- DeLong EF, Pace NR (2001). "Environmental diversity of bacteria and archaea". Syst. Biol. 50 (4): 470–8. Full text: .