Canadian Medical Guide > Organisms > Archaea Terms and Definitions

Archaea

Medical Definition:	One of the three domains of life (the others being BACTERIA and Eucarya), formerly called Archaebacteria under the taxon Bacteria, but now considered separate and distinct. They are characterized by: (1) the presence of characteristic tRNAs and ribosomal RNAs; (2) the absence of peptidoglycan cell walls; (3) the presence of ether-linked lipids built from branched-chain subunits; and (4) their occurrence in unusual habitats. While archaea resemble bacteria in morphology and genomic organization, they resemble eukarya in their method of genomic replication. The domain contains at least three kingdoms: CRENARCHAEOTA; EURYARCHAEOTA; and KORARCHAEOTA.
Guide Notes:	in taxonomy, one of the 3 domains of life along with BACTERIA & Eucarya
Previously Indexed:	Bacteria (1966-1980)

Archaea Categories.

	Crenarchaeota - A kingdom in the domain ARCHAEA comprised of thermoacidophilic, sulfur-dependent organisms. The two orders are SULFOLOBALES and THERMOPROTEALES.
	Euryarchaeota - A phylum of ARCHAEA comprising at least seven classes: Methanobacteria, Methanococci, Halobacteria (extreme halophiles), Archaeoglobi (sulfate-reducing species), Methanopyri, and the thermophiles: Thermoplasmata, and Thermococci.
	Korarchaeota - A kingdom in the domain ARCHAEA, comprising thermophilic organisms from the hot spring Obsidian Pool (Yellowstone National Park) that are among the most primitive of all life forms. They have undergone comparatively little evolutionary change since the last common ancestor of all extant life. (From ASM News, 1996; 62(9):468-9)

Archaea Medical Definitions and Terms

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