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.
Archaebacteria are found in very harsh conditions such as in the volcanic vents or at the bottom of the sea. They. are often called  extremophiles . They can easily survive in such extreme environment as sea vents releasing sulfideârich gases, hot springs, or boiling mud around volcanoes.