Chemical substances may be combined or converted to others by means of chemical reactions. Forms of energy, such as light and heat, are not matter, and are thus not substances in this regard.
Halophiles are organisms that thrive in high salt concentrations. They are a type of extremophile organism. The name comes from the Greek word for salt-loving. While most halophiles are classified into the Archaea domain, there are also bacterial halophiles and some eukaryota, such as the alga Dunaliella salina or fungus Wallemia ichthyophaga. Some well-known species give off a red color from carotenoid compounds, notably bacteriorhodopsin.
The organisms also developed a defense mechanism that protected them from cold temperatures. The halophiles and methanogens are part of a hardy group of microbes called extremophiles, which thrive in the harshest environments on Earth. Maryland Astrobiology Consortium/NASA/STScI. These close-up images, taken by an electron microscope, reveal tiny one-cell organisms called halophiles and methanogens.