Archaea

Archaea are single-celled organisms in one of the three domains of life. They lack a nucleus but differ from bacteria in their evolutionary history and distinctive cellular machinery.

Archaeal cell membrane: A membrane built from ether-linked lipids, often with branched isoprenoid chains. Its unusual lipid chemistry distinguishes archaeal membranes from bacterial and eukaryotic membranes.
Methanogenesis: The biological production of methane by certain archaea using carbon dioxide, acetate, or other substrates. This metabolism is known only among archaea.
Carl Woese: An American microbiologist who established molecular phylogeny using ribosomal RNA comparisons. His comparisons revealed that archaea form a domain distinct from bacteria.
Taq polymerase: A heat-stable DNA polymerase from the bacterium Thermus aquaticus, widely used in PCR. It popularized thermostable enzymes; archaeal polymerases offer alternatives with proofreading activity.
Archaeal cell wall: The external cell layer of many archaea, commonly made from protein or glycoprotein rather than bacterial peptidoglycan. Its varied materials show that archaeal walls do not follow the bacterial pattern.
Chemolithotrophy: A mode of metabolism that obtains energy by oxidizing inorganic compounds. Many archaea use inorganic chemicals as energy sources in oxygen-poor or extreme habitats.
Three-domain system: A classification of cellular life into Bacteria, Archaea, and Eukarya. Archaea are one of the three domains in the system Woese proposed.
Pfu polymerase: A thermostable DNA polymerase from the archaeon Pyrococcus furiosus with proofreading activity. Its archaeal origin provides a high-fidelity enzyme for DNA amplification.
Archaeal ribosome: A ribonucleoprotein complex that translates messenger RNA into proteins in archaeal cells. Its proteins and translation factors resemble eukaryotic counterparts more than bacterial ones.
Archaeal ammonia oxidation: The oxidation of ammonia to nitrite by ammonia-oxidizing archaea. These archaea drive a major step in the global nitrogen cycle.

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