Archaea facts for kids

Archaea (Archaebacteria) Temporal range: 3.5-0Ga Had'n <div style="position:absolute; height:12px; top:6px; text-align:center; background-color:rgb(238,0,125); left:32.608695652174px; width:px;"> Archean Proterozoic Pha. Paleoarchean or perhaps Eoarchean – recent
Halobacterium sp. strain NRC-1, each cell about 5 μm long
Scientific classification
Domain:	Archaea Woese, Kandler & Wheelis, 1990
Kingdoms and phyla
"Euryarchaeota" Woese et al. 1990 "Methanopyri" Garrity and Holt 2002 "Methanococci" Boone 2002 "Eurythermea" Cavalier-Smith 2002 "Neobacteria" Cavalier-Smith 2002 "DPANN" "ARMAN" "Micrarchaeota" Baker et al. 2010 "Parvarchaeota" Rinke et al. 2013 "Aenigmarchaeota" Rinke et al. 2013 "Diapherotrites" Rinke et al. 2013 "Nanoarchaeota" Huber et al. 2002 "Nanohaloarchaeota" Rinke et al. 2013 "Pacearchaeota" Castelle et al. 2015 "Woesearchaeota" Castelle et al. 2015 "Proteoarchaeota" Petitjean et al. 2015 (TACK)"Filarchaeota" Cavalier-Smith, T. 2014 "Aigarchaeota" Nunoura et al. 2011 "Bathyarchaeota" Meng et al. 2014 Crenarchaeota Garrity & Holt 2002 "Geoarchaeota" Kozubal et al. 2013 "Korarchaeota" Barns et al. 1996 Thaumarchaeota Brochier-Armanet et al. 2008 "Asgardarchaeota" Violette Da Cunha et al., 2017 "Lokiarchaeota" Spang et al. 2015 "Thorarchaeota" Seitz et al. 2016 "Odinarchaeota" Katarzyna Zaremba-Niedzwiedzka et al. 2017 "Heimdallarchaeota" Katarzyna Zaremba-Niedzwiedzka et al. 2017
Synonyms
Archaebacteria Woese & Fox, 1977 Mendosicutes Gibbons & Murray, 1978 Metabacteria Hori and Osawa 1979

Colourful archaea at Midway geyser

The Archaea (or Archea) are a group of single-celled organisms. The name comes from Greek αρχαία, "old ones". They are a major division of living organisms.

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.

Archaea are, like bacteria, prokaryotes: single-celled organisms that do not have nuclei and cell organelles of the eukaryote type.

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.

Property	Archaea	Bacteria	Eukarya
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

= Interesting facts about archaea:

• 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.

Related pages

• Carl Woese
• Earliest known life forms
• Methanogen

• 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

Images for kids

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  Archaea were found in volcanic hot springs. Pictured here is Grand Prismatic Spring of Yellowstone National Park.
  

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  The ARMAN are a group of archaea recently discovered in acid mine drainage.

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  Bacteriorhodopsin from Halobacterium salinarum. The retinol cofactor and residues involved in proton transfer are shown as ball-and-stick models.

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  Sulfolobus infected with the DNA virus STSV1. Bar is 1 micrometer.

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  Archaea that grow in the hot water of the Morning Glory Hot Spring in Yellowstone National Park produce a bright colour

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  Methanogenic archaea form a symbiosis with termites.