Archaea
domain of prokaryotic microorganisms
Archaea ( ar-KEE-ə) is a domain of organisms. Traditionally, Archaea included only its prokaryotic members, but has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even though the domain Archaea cladistically includes eukaryotes, the term archaea (sing. archaeon ar-KEE-on; from Ancient Greek ἀρχαῖον arkhaîon 'ancient') in English still generally refers specifically to prokaryotic members of Archaea.
Archaea were initially classified as bacteria, receiving the name archaebacteria (, in the Archaebacteria kingdom), but this taxonomic approach has fallen out of use. Archaeal cells have unique properties distinguishing them from Bacteria and Eukaryota, including: cell membranes made of ether-linked lipids; metabolisms such as methanogenesis; and a unique motility structure known as an archaellum. Archaea are further divided into multiple recognized phyla. Classification is difficult because most have not been isolated in a laboratory and have been identified only by their gene sequences in environmental samples. They have not been observed to produce endospores.
Archaea are often similar to bacteria in size and shape, although a few have very different shapes, such as the flat, square cells of Haloquadratum walsbyi. Despite this, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably for the enzymes involved in transcription and translation.
The public source identifies “Archaea” as domain of prokaryotic microorganisms. This brief keeps that definition visible, then builds a research path around Archaea, domain and prokaryotic.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 6, 2026. The linked authority identifier is Q10872. The Library of Congress control number is sh86006229. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank.
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This entry incorporates text from “Archaea” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.