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.
Ancient methanogens are the source of natural gas. Halophiles are bacteria that thrive in high salt concentrations such as those found in salt lakes or pools of sea water. Thermophiles are the heat-loving bacteria found near hydrothermal vents and hot springs.
Like the methanogens and sulfur reducers, these archaebacteria live near volcanic vents and pools and thus are adapted to high temperatures (65 to 80 degrees Celsius). Unlike the other two classes, though, thermoacidophiles also prefer extremely acidic conditions, living in environments with a pH as low as 1.0.