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 first type is called Methanogens. 1  This type of Archaebacteria live in oxegen free enviornments and they produce Methane gasess. 2  Places methangogens can be found are: marshes, lake sediments, and digestive tracts of animals. 3  Commercial use: used in sewage plant to help breakdown sewage.