the hard, variously colored, calcareous skeleton secreted by certain marine polyps. 2. such skeletons collectively, forming reefs, islands, etc. 3. the solitary or colonial polyp that secretes this calcareous skeleton.
There are three major known groups of Archaebacteria: methanogens, halophiles, and thermophiles. The methanogens are anaerobic bacteria that produce methane. They are found in sewage treatment plants, bogs, and the intestinal tracts of ruminants.
Archaebacteria are part of the prokaryotic organism family, which means they are tiny, single-celled organisms. According to the State University of New York, they are plentiful in water, air and on objects. There are three different types of archaebacteria, and all make their home in extreme environments.