The kingdom Archaebacteria
(or domain Archaea)

The kingdom Archaebacteria has been regarded by some as merely a very ancient group within a single kingdom of prokaryotic organisms, the Monera. Others regard the Archaebacteria as so fundamentally different from other prokaryotes in details of their structure (e.g. of the plasma membranes), that it is misleading to call them bacteria at all, a view supported by DNA studies.

Many inhabit environments so extreme that it is hardly credible that they can contain life, though such environments were prevalent in the primaeval conditions when prokaryotes first evolved. Some archaeans are strict anaerobes, reducing carbon dioxide to methane, others are extreme halophiles, while still others can survive in hot sulphur springs. Potentially some can exist wherever water penetrates and sulphide minerals provide an energy source, even at some depth into the Earth's crust.

hot springs at Geysir, Iceland
Hot springs at Geysir, Iceland: home of archaean extremophiles. Eruptions shower the ground every few minutes with super-heated, sulphide-rich water.

While in many ways strange, and challenging our ideas of where life can exist, it is the Archaea rather than the Bacteria that should be considered the ancestors of eukaryotic life, including ourselves. Our evolutionary connection to the more familiar bacterial prokaryotes is only through the ancient bacteria that were engulfed by equally ancient archeans, bacteria that then persisted by 'endosymbiosis', eventually to become the mitochondia and, in plants, chloroplasts and other plastids, of present day eukaryotic cells.

In the context of these biodiversity pages, where the primary aim is to provide illustrative images, it is not anticipated that there will be much opportunity to develop this section further. Accounts of this group should be found in modern textbooks, while useful Web summaries can be found by following the links below.

Links to further information

Introduction to the Archaea
(UC Museum of Paleontology, Berkeley)
Brief but useful account (which rejects the name "Archaebacteria").

The Tree of Life Project Root Page
(David R. Maddison and Wayne P. Maddison, University of Arizona)
Provides differing views on the evolutionary position of the Archaea and a valuable listing of literature references.

A.J. Silverside, January 2010
Originally developed as a teaching resource for the University of Paisley (now the University of the West of Scotland),
first hosted at, September 1998
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