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AArchaea

A prokaryotic domain that is not bacteria — methanogens, extremophiles and no known human pathogens.

Also called: Archaebacteria (obsolete name) ? Third domain

OverviewIdentityHow they liveBody & healthHistoryEveryday lifeFrontiersMyths
11 min read Frequently asked questions

Reviewed 2026-08·Sources & research·Media credits

Haloarchaea in a salt pond appearing pink-purple
Maulucioni ? CC BY-SA 4.0

Quick facts

Archaea — not BacteriaDomain
1977 — Woese and Fox, 16S rRNASplit proposed
Ether-linked isoprenoid lipidsMembrane cue
No peptidoglycanCell wall
None knownHuman pathogens
Methanogenesis is archaeal-onlySignature metabolism

Archaea are prokaryotes that are not bacteria. Ether lipids, distinct ribosomes and methanogenesis mark a domain Carl Woese peeled off the old 'bacteria' bag in 1977.

Famous species love heat, acid or salt, but the domain also fills oceans and the human gut. No archaeon is a known human pathogen.

This atlas treats archaea as a tree-of-life branch, not a synonym for 'extreme germ'. Methane, climate and eukaryote origins sit in later sections.

The profile

35225587020
  • Familiarity35
  • Medical weight22
  • Benefit55
  • Risk8
  • Research70
  • Live debate20

Risk

8 / 100

A prokaryotic domain that is not bacteria — methanogens, extremophiles and no known human pathogens.

Seven ways into this topic

01

Identity

A third domain of prokaryotes — not bacteria — with unique membranes and no known human pathogens.

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 02

How they live

Unique membranes, methanogenesis, archaeal viruses and slow environmental growth.

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 03

Body & health

Gut methanogens are residents, not invaders. No archaeal species is a known human pathogen.

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 04

History

From 'archaebacteria' to a third domain, methanogen biochemistry and Lokiarchaeota.

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 05

Everyday life

Marsh gas, rice paddies, salt foods and the microbes you never see on a 'germ' poster.

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 06

Frontiers

Eukaryote origins, uncultured marine clades and climate roles of methane.

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 07

Myths

Not bacteria, not automatically extreme, not a human plague.

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Frequently asked questions

Are archaea bacteria?
No. Both lack a nucleus, but membranes, ribosomes and many genes differ. They are a separate domain.
Do archaea infect people?
No species is an established human pathogen. Gut methanogens are residents, not invaders.
Why were they called archaebacteria?
An old name assumed they were odd bacteria. The name stuck in some textbooks after the science moved on.
Do they only live in extremes?
No. Oceans, soils and animal guts host huge archaeal populations.
What is a methanogen?
An archaeon that makes methane from CO2, hydrogen or simple organics. Bacteria do not run this pathway.
Are they older than bacteria?
The name sounds ancient; both domains are deep. 'Older' is a tree argument, not a fossil slogan.
Can I culture them at home?
This atlas does not give culture methods. Many archaea need unusual gases or salts best left to labs.
Is this medical advice?
No. Educational only. There is no archaeal infection chapter for a clinician to treat as strep.

Sources & research

  1. Archaea2026 · Wikipedia
  2. Woese & Fox 19771977 · PNAS

Media credits

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