An extremophile is an organism (a living thing) that lives best in extreme conditions that are harmful to most life on Earth. They are different from organisms that live in medium temperatures or places that have a neutral pH. These organisms can be called mesophiles or neutrophiles.
In the 1980s and 1990s, biologists found that microbes can survive in extreme environments. These are niches that are extreme in some way. They may be extremely hot, or cold, or dry, or under huge pressures, or very salty or acidic. Complex orgamisms, such as cats, trees, and people, cannot live in these environments. Some scientists suggest that life may have begun on Earth in hydrothermal vents far below the ocean surface. Very hot environmetns such as hot oceans, hot springs and deep ocean hydrothermal vents would have been very, very common during a time called the Archaean eon, which was about 3.9 billion years ago. Early forms of life had to adapt (become able to survive) to these environments in order to survive and become bigger and stronger.
Types of extremophiles[change | change source]
Most known extremophiles are microbes. The domain Archaea has well-known examples of extremophiles, but some bacteria can be extremophiles as well. It is a mistake to use the term extremophile for all archaeans, because some of them are mesophilic. Also, not all extremophiles are unicellular; some extreme environments have animals that are protosomes (they are made up of many cells).
Some extremophiles fall under several categories. For example, organisms living inside hot rocks deep under Earth's surface are both thermophilic and barophilic.
- An organism that grows best at pH levels of 3 or below.
- An organism that grows best at pH levels of 9 or above
- An organism that lives in microscopic spaces within rocks, fissures, aquifers, and faults filled with groundwater deep under the ground.
- An organism that needs lots of salt to grow.
- An organism that can live well at temperatures between 80–122 °C, such as those found in hydrothermal vents in the deep ocean.
- An organism that lives inside rocks in cold deserts.
- An organism (usually bacteria) that only gets carbon from carbon dioxide and oxidation (these organisms can be called chemolithotrophs). These organisms can get energy from mineral compounds such as pyrites, and can use geochemical cycling and the wearing away of bedrock to form soil.
- These organisms are not harmed by high levels of dissolved heavy metals in solution, such as copper, cadmium, arsenic, and zinc.
- An organism that can grow in environments with very few nutrients.
- An organism that can grow in environments with lots of sugar.
- An organism that lives best under high pressure, such as deep inside the earth's surface and is trenches deep in the ocean.
- An organism that is in more than one category of extremophiles, such as an organism that is both a xerophile (can grow in extremely dry places) and an oligotroph (can grow in places with very few nutrients).
- An organism that grows better at temperatures of 15 °C or lower; such as in cold soils, permafrost, polar ice, cold ocean water, and in snow in high mountains.
- Organisms that can resist (put up with) high levels of ionizing radiation, like ultraviolet or nuclear radiation, that harms other organisms by giving them cancer or burning them.
- An organism that can live well at temperatures between 60–80 °C.
- An organism that is both a thermophile and an acidophile. It grows best in temperatures of 70–80 °C and pH between 2 and 3.
- An organism that can grow in extremely dryplaces, such as the Atacama Desert.
References[change | change source]
- "Mars Exploration - Press kit" (PDF). NASA. June 2003. http://marsrovers.jpl.nasa.gov/newsroom/merlaunch.pdf. Retrieved 2009-07-14.
- Gouy M. & Chaussidon M. 2008. Ancient bacteria liked it hot. Nature 451: p635.
- Cavicchioli R. & Thomas T. 2000. Extremophiles. In: J. Lederberg (ed) Encyclopedia of Microbiology, 2nd ed, Vol 2, pp317–337. Academic Press, San Diego.