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 organisms that are actually very different biochemically and genetically from other bacteria. Hence, archaebacteria is an outdated term, and they are now classified in the Archaea domain. Classifications within this domain are unofficial due to debates over the descendancy of microbes.ence, archaebacteria is an outdated term, and they are now classified in the Archaea domain. Classifications within this domain are unofficial due to debates over the descendancy of microbes.