What does eubacterium mean?
Eubacterium is a noun denoting what biologists once called a 'true bacterium': any prokaryotic microorganism belonging to the group traditionally known as the Eubacteria. The prefix 'eu-', from Greek meaning 'good' or 'true', distinguished these organisms from the archaebacteria, a superficially similar group of prokaryotes recognized as biochemically distinct in the late twentieth century. Under older classification schemes, such as the five-kingdom system, all life without a nucleus was sorted into eubacteria or archaebacteria. With the adoption of the three-domain system proposed by Carl Woese, however, the distinction became obsolete: the eubacteria were renamed simply bacteria, forming the domain Bacteria, while the archaebacteria became the archaea. Today 'eubacterium' survives mainly in historical, pedagogical, and some taxonomic contexts, and readers encountering it should understand it as an older label for ordinary bacteria rather than a separate category of organism.
nounA eubacterium is a bacterium of the group formerly classified as Eubacteria — true bacteria, as distinct from archaebacteria (archaea). The term is now largely historical, having been superseded by 'bacterium' after the three-domain system separated bacteria from archaea.
- A prokaryotic microorganism belonging to the former kingdom Eubacteria, i.e. a true bacterium as opposed to an archaebacterium; now usually called simply a bacterium.
"Under the older two-empire scheme, every microorganism lacking a nucleus was assigned either to the Eubacteria or to the Archaebacteria."
"The textbook's chapter on the Monera divided prokaryotes into the eubacteria and the archaebacteria."
"Peptidoglycan is found in the cell walls of nearly all eubacteria but is absent in archaea."
Standard Latin-style plural. Note that 'Eubacteria' capitalized was also used as the name of the taxonomic group itself, functioning as a collective singular.
"Most eubacteria reproduce by binary fission."
'Eubacterium' literally means 'true bacterium' — a name that made perfect sense until scientists discovered that bacteria and archaea are as different from each other as each is from us.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eubacterium
The word combines the Greek prefix 'eu-' ('good', 'well', 'true') with 'bacterium', itself borrowed in the nineteenth century from New Latin, ultimately from Greek 'bakterion', a diminutive of 'baktron' meaning 'staff' or 'rod', referring to the rod-like shape of many bacteria. 'Eubacterium' was coined in the twentieth century to distinguish true bacteria from the newly recognized archaebacteria, mirroring earlier formations such as 'eukaryote'. Following Carl Woese's three-domain classification, developed from ribosomal RNA studies in the late 1970s and widely adopted thereafter, the term fell out of favor in favor of plain 'bacterium'. Cognates sharing the 'eu-' root include 'euphoria', 'eulogy', and 'eugenics'.
How eubacterium is actually used
The term is chiefly historical and scientific, used when discussing older classification schemes such as the five-kingdom or two-empire systems. In modern taxonomy the word has largely fallen out of use: organisms once called eubacteria are now simply called bacteria. The plural 'eubacteria' was also used as the name of the group itself.
Easily confused with eubacterium
An archaebacterium (archaeon) belongs to the separate domain Archaea, whereas a eubacterium is a 'true' bacterium of the domain Bacteria.