What does archaebacterium mean?
An archaebacterium is a single-celled microorganism belonging to a group of prokaryotes once classified as a kingdom called Archaebacteria and now generally placed in their own domain, Archaea. Like bacteria, archaebacteria lack a cell nucleus, but they differ fundamentally in their genetics, cell wall chemistry, and membrane lipids — differences so deep that microbiologist Carl Woese proposed splitting life into three domains: Bacteria, Archaea, and Eukarya. Many archaebacteria are extremophiles, flourishing in environments hostile to most life, such as boiling hot springs, hypersaline lakes, acidic mine drainage, and hydrothermal vents on the ocean floor; others, known as methanogens, produce methane in wetlands and animal digestive tracts. The singular form 'archaebacterium' appears mainly in older or textbook usage, while the plural 'archaebacteria' and the modern terms 'archaeon' and 'archaea' are more common today. The word remains useful shorthand for discussing these remarkable organisms and the history of how biologists reorganized the tree of life around them.
nounA prokaryotic microorganism of the kingdom (or domain) Archaebacteria, now usually classified as Archaea; single-celled organisms that lack a nucleus and typically live in extreme environments such as hot springs, salt lakes, and deep-sea vents.
- A single-celled prokaryotic microorganism belonging to the group Archaebacteria (now classified as the domain Archaea), often characterized by survival in extreme environments.
- In older biological classification, a member of the kingdom Archaebacteria, distinguished from Eubacteria by cell wall composition and ribosomal RNA.
"The hot spring teemed with archaebacteria thriving at temperatures that would kill most other organisms."
"Methanogens, a type of archaebacterium, produce methane in the digestive tracts of cattle."
"Carl Woese's research on ribosomal RNA showed that archaebacteria form a lineage entirely separate from true bacteria."
The plural 'archaebacteria' is far more common than the singular, since the organisms are almost always discussed as a group.
"Archaebacteria inhabit some of the most inhospitable environments on Earth."
Archaebacteria were once lumped in with ordinary bacteria until genetic studies revealed they are so different that scientists had to redraw the tree of life itself.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of archaebacterium
The word derives from Greek elements: 'archaios', meaning ancient or primitive, combined with 'bakterion', the Greek diminutive meaning small rod, which also gave English 'bacterium'. The term was coined in the twentieth century when microbiologists recognized a distinct group of prokaryotes that seemed more primitive than typical bacteria. Related words sharing the Greek root include 'archaic', 'archaeology', and 'archive'. Following Woese's three-domain system, the newer term 'archaeon' was introduced to replace it.
Related word forms
How archaebacterium is actually used
This is a formal scientific term used mainly in biology textbooks and older literature. In contemporary taxonomy, 'archaebacterium' has largely been replaced by 'archaeon' (plural 'archaea'), following Carl Woese's three-domain system introduced in 1990. The plural 'archaebacteria' is more frequently encountered than the singular form.
Easily confused with archaebacterium
Bacterium refers to true bacteria (Eubacteria), whereas archaebacterium denotes a genetically distinct group of prokaryotes now placed in their own domain, Archaea.
Archaea is the modern taxonomic name for the same group of organisms, while archaebacterium is the older term still used in many textbooks.