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.
The eubacteria and archaebacteria are probably the least known of this categorization. Eubacteria and archaebacteria are two very different kinds of bacteria, each with their own identities and use in our daily lives. Archaebacteria are one of the oldest of organisms found on planet earth.