Archaea
Say it: ahr-KEE-uh
Archaea are single-celled prokaryotes that form their own domain of life, distinct from bacteria in their membranes, cell walls and genes.
Also: archaeon, archaebacteria
Definition
What are archaea?
Archaea are microscopic, single-celled organisms that make up one of the three domains of life, alongside Bacteria and Eukarya. Like bacteria they are prokaryotes, with no nucleus and no membrane-bound organelles, and under a microscope the two often look alike. In the 1970s Carl Woese and his colleagues compared ribosomal RNA sequences and showed that archaea form a separate lineage, which was first called archaebacteria.
Archaea differ from bacteria in their basic chemistry. Their membrane lipids are made of branched isoprene chains attached by ether bonds, unlike the ester-linked, unbranched fatty acids of bacteria and eukaryotes, which helps some of them survive extreme heat. Their cell walls never contain peptidoglycan; some have a similar material called pseudopeptidoglycan, and others have protein or sugar layers. One group, the methanogens, produces methane, a kind of metabolism that no bacterium or eukaryote carries out.
Many archaea are extremophiles that thrive in boiling hot springs, very salty lakes or acidic water, but others are common in ordinary soil, the open ocean and animal guts. None is currently known to cause infectious disease in humans or other organisms.
Word parts
Where does the word “archaea” come from?
- archae-
- ancientGreek archaios
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Related
Terms that go with it
- ProkaryoteA prokaryote is a usually single-celled organism, a bacterium or an archaeon, whose cell has no nucleus or other membrane-bound organelles.
- BacteriumA bacterium is a single-celled prokaryote with no nucleus, found in almost every habitat on Earth, including in and on the human body.
- EukaryoteA eukaryote is an organism whose cells keep their DNA inside a membrane-bound nucleus and contain other membrane-bound organelles.
- Cell membraneThe cell membrane is the thin, flexible boundary of lipids and proteins that encloses every cell and controls what enters and leaves it.
- PeptidoglycanPeptidoglycan is the mesh-like polymer of sugars and short peptides that forms the bacterial cell wall and gives bacteria their shape and strength.
- Phylogenetic treeA phylogenetic tree is a branching diagram that shows the evolutionary relationships among organisms or genes as a hypothesis of shared descent.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Microbiology, 4.6 Archaea
- UC Museum of Paleontology: Introduction to the Archaea
- Dictionary.com: archaea
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