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 microscopic organisms with diameters ranging from 0.0002â0.0004 in (0.5â1.0 micrometer). The volume of their cells is only around one-thousandth that of a typical eukaryotic cell. They come in a variety of shapes, which can be characterized into three common forms.