Title: archaea | Definition, Characteristics, & Examples | Britannica
Headings: Archaea
Archaea
prokaryote
Habitats of the archaea

Content: archaea | Definition, Characteristics, & Examples | Britannica
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Archaea
prokaryote
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WRITTEN BY
Thomas Niederberger
Postdoctoral fellow, Natural Resource Sciences, Microbiology, McGill University. See Article History
Alternative Titles: Archaea, archaean, archaebacteria, archaebacterium, archaeobacteria, archaeobacterium, archaeon
Archaea, (domain Archaea), any of a group of single-celled prokaryotic organisms (that is, organisms whose cells lack a defined nucleus) that have distinct molecular characteristics separating them from bacteria (the other, more prominent group of prokaryotes) as well as from eukaryotes (organisms, including plants and animals, whose cells contain a defined nucleus). Archaea is derived from the Greek word archaios, meaning “ancient” or “primitive,” and indeed some archaea exhibit characteristics worthy of that name. Members of the archaea include: Pyrolobus fumarii, which holds the upper temperature limit for life at 113 °C (235 °F) and was found living in hydrothermal vents; species of Picrophilus, which were isolated from acidic soils in Japan and are the most acid-tolerant organisms known—capable of growth at around pH 0; and the methanogens, which produce methane gas as a metabolic by-product and are found in anaerobic environments, such as in marshes, hot springs, and the guts of animals, including humans. archaea
Archaea are found in a diverse range of extreme environments, including the salt deposits on the shores of the Dead Sea. Z. Radovan, Jerusalem
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