Archaea Kids Encyclopedia

Archaea Temporal range: Archaean – Recent
Halobacteria sp. strain NRC-1, each cell about 5 μm long.
Scientific classification
Domain:	Archaea Woese, Kandler & Wheelis, 1990
Kingdoms and phyla
Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota Thaumarchaeota

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 classification 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.

Interesting facts

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 by 1978, and proved it was a separate Kingdom by 1990.

Related pages

• Methanogen

Images

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  Archaea were first found in extreme environments, such as volcanic hot springs. Pictured here is Grand Prismatic Spring of Yellowstone National Park.

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

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  Diagrammatic view of Methanobrevibacter smithii, showing the cell membrane (ochre, with inset) and cell wall (purple).

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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.