Archaeon

Scientists investigating smokers, vents on the ocean floor which spew hot seawater rich in dissolved minerals, were startled to discover in the early eighties that they were home for bacteria-like organisms. They are almost the only living things on Earth which survive independently of heat and light from the Sun and thrive at temperatures near the boiling point of water, which would kill any other organism. These bacteria were at first called archaebacteria (from the Greek archaeos, “ancient”), but more recently the term archaeon (plural archaea; also spelled archeon and archea) has come into use, recognising their unique place in evolution as a third type of organism, separate from the eucaryotes and bacteria. The archaea are believed to be living fossils surviving from a time when the Earth had little oxygen in its atmosphere. Other examples have been found in sewage sludge, rubbish tips and in cracks in rocks deep in the earth. The complete genome of one such has just been sequenced.