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n. pl. ar·chae·a (-kē-ə)
Any of various prokaryotic microorganisms of the domain Archaea, being genetically distinct from bacteria and often living in habitats with extreme environmental conditions such as high temperature or salinity. Also called archaebacterium.

[New Latin Archaeon (back-formed singular of Archaea, domain name), from Greek arkhaion, neuter singular of arkhaios, ancient (in reference to the very ancient separation of the archaea and the eubacteria in evolutionary history); see archaic.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


an order of prokaryotic microorganisms
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
The organism is based on a member of the Archaea microbes found in 2010 in a sediment core from the Arctic ocean.
Two kinds of cells then developed, one into bacteria the other into archaea. Both lacked nuclei but they were certainly alive.
The 2018 edition of the annual series describes the structure and function of thin membrane protrusions, organelle formation in bacteria and archaea, transpeptidases for modifying proteins, unconventional ways in which cells have evolved to die or survive, positioning of the oocyte meiotic spindle, and axon regeneration in the central nervous system.
This environment, therefore, facilitates the assembly of a community of archaea and is different from other anoxic habitats.
Early life on Earth started at the microbial level, with basic single-celled microorganisms like bacteria and archaea. Later came the eukaryote domain which included complex cellular organisms like humans, animals, plants, and fungi.
"We tried to reproduce the putative Enceladus-like conditions in the lab," said Simon Rittmann, who studies microbes called archaea at the University of Vienna in Austria.
However, recently it was found that ammonia-oxidising archaea (AOA) may also play an important role in ammonia oxidation (Lcininger et al.
In many applications where Bacteria are the key players in bioremediation, however, Archaea are often involved as well.
The study looked at protein structures in viruses and across all superkingdoms, or domains, of life: from the single-celled microbes known as bacteria and archaea, to eukaryotes, a group that includes animals, plants, fungi and all other living things.
It can analyze 96 samples in parallel, with each sample being exposed to 1.4 million DNA probes that have been designed to detect over 12,000 unique microbial species-including all bacteria, viruses, fungi, archaea, and protozoa--with at least one genome previously sequenced and publicly available as of the probe design date.
Archaea is one of the three domains of life which encompass organisms that live in extreme environments, such as strict anaerobic conditions, high temperature, and high salinity.