Archaea versus Eubacteria

Traditional classification schemes separated organisms into two main groups – prokaryotes and eukaryotes

  • This classification scheme was widely entrenched until 1977 when Carl Woese proposed a new system

The large diversity of organisms classified as prokaryotes prompted Woese to separate these bacteria into two distinct domains

  • Eubacteria includes most of the commonly encountered bacterial forms (i.e. pathogenic bacteria and probiotic bacteria)
  • Archaea consists of the extremophiles (e.g. thermophiles, halophiles, methanogens, etc.)

The archaeal cells were found to possess certain features that were more in common with eukaryotic cells than eubacteria

  • This included certain structural features (e.g. cell wall composition) and the presence of histone-like proteins in DNA
  • Based on these discoveries it was concluded that eukaryotes and archaea share more recent common ancestry than eubacteria

Comparison of Archaea, Eubacteria and Eukarya

archaea vs eubacteria

Evolutionary History of the Three Domains

archaea phylogeny