archaebacteria

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Archaea

Evolutionary biology
One of the three domains of living organisms: Archaea, Bacteria and Eukaryota. While Archaea are single-celled, they are unlike bacteria given their independent evolutionary history. Archaea differ from Eukaryota in their ribosomal structure and the presence—in some—of introns in the genome, as well as other features (e.g., different membrane composition).
 
Molecular biology
Archaea are of interest in biotechnology as they have unique biochemical features (e.g., enzymes of theromophiles, such as Taq polymerase, the “workhorse” enzyme of PCR) and are extremely stable at high temperatures. Archaea include metabolic oddities (e.g., extreme halophiles, which live in extremely salty environments), methanogens (which produce methane) and sulphur-dependant extreme thermophiles (which can live in extremely hot environments).

Archaea phyla
• Crenarchaeota
• Euryarchaeota
• Korarchaeota
• Nanoarchaeota
• Thaumarchaeota (recently proposed)

ar·chae·bac·ter·i·a

(ahr'kē-bak-tēr'ē-ā)
A group of microorganisms that thrive in the absence of oxygen, produce methane, and live only in bodies of highly concentrated salt water, or in the acidic waters of sulfur springs, at temperatures near 80° Celsius and pH levels as low as 2.

Archaebacteria)

one of the three primary groupings (DOMAINS) of ORGANISMS, according to some classification schemes, based on genetic structures and sequences. See CLASSIFICATION. Members of the Archaea are PROKARYOTES and include the extreme HALOPHILES, the thermoacidophiles (organisms that normally grow at high temperatures in acidic environments; see also THERMOPHILIC), and the METHANOGENS.

They differ in a number of ways from other BACTERIA, for example in the structure of their MEMBRANE LIPIDS, TRANSFER RNA molecules and CELL WALL, and in their sensitivity to ANTIBIOTICS. The Archaea is a very diverse group organized into two KINGDOMS, the CRENARCHAEOTA and the EURYARCHAEOTA. It was initially considered to represent the most ancient group of organisms still living. This is reflected in the name, from the Greek archaios, meaning ancient.

archaebacteria

prokaryotic organisms, distinct from eubacteria, which are found in association with high temperatures or salinity, or are methanogenic. None are pathogens.
References in periodicals archive ?
An archaebacterial promoter element for stable RNA genes with homology to the lATA box of higher eukaryotes.
The strong resemblances of these same enzymes among the major eubacterial groups suggest that the cyanobacteria, gram-positive and gram-negative eubacteria also diverged at about the same time, whereas the much greater differences between archaebacterial and eubacterial sequences indicate these two groups may have diverged between three and four billion years ago.
I think it is, therefore, incumbent on people in this field who are going to push for this as a new group, to go out and provide other evidence, to get other gene sequences to substantiate or refute the idea that this is a fundamentally new group of archaebacterial life.