Extremophile

An extremophile is an organism that thrives in and may even require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth.

Most known extremophiles are microbes. The domain Archaea contains renowned examples, but extremophiles are present in numerous and diverse genetic lineages of both bacteria and archaeans. Furthermore, it is erroneous to use the term extremophile to encompass all archaeans, as some are mesophilic. Neither are all extremophiles unicellular; protostomes found in similar environments include the Pompeii worm, the psychrophilic Grylloblattodea (insects), Antarctic krill (a crustacean) and the "water bear".

Types of extremophiles

There are many different classes of extremophiles, each corresponding to the way its environmental niche differs from mesophilic conditions. These classifications are not exclusive. Many extremophiles fall under multiple categories. For example, organisms living inside hot rocks deep under Earth's surface are both "thermophilic" and "barophilic".
* Acidophile: An organism with an optimum pH level at or below pH 3.
* Alkaliphile: An organism with optimal growth at pH levels of 9 or above.
* Endolith: An organism that lives in microscopic spaces within rocks, such as pores between aggregate grains. These may also be called cryptoendoliths. This term also includes organisms populating fissures, aquifers, and faults filled with groundwater in the deep subsurface.
* Halophile: An organism requiring at least 2M of salt, NaCl, for growth.
* Hyperthermophile: An organism that can thrive at temperatures between 80-122 °C, such as those found in hydrothermal systems.
* Hypolith: An organism that lives inside rocks in cold deserts.
* Lithoautotroph: An organism (usually bacteria) whose sole source of carbon is carbon dioxide and exergonic inorganic oxidation (chemolithotrophs) such as "Nitrosomonas europaea". These organisms are capable of deriving energy from reduced mineral compounds like pyrites, and are active in geochemical cycling and the weathering of parent bedrock to form soil.
* Metalotolerant: capable of tolerating high levels of dissolved heavy metals in solution, such as copper, cadmium, arsenic, and zinc. Examples include "Ferroplasma sp." and "Ralstonia metallidurans".
* Oligotroph: An organism capable of growth in nutritionally limited environments.
*Osmophile: An organism capable of growth in environments with a high sugar concentration.
* Piezophile: An organism that lives optimally at high hydrostatic pressure. Common in the deep terrestrial subsurface, as well as in oceanic trenches.
* Polyextremophile: An organism that qualifies as an extremophile under more than one category.
* Psychrophile/Cryophile: An organism that grows better at temperatures of 15 °C or lower. Common in cold soils, permafrost, polar ice, cold ocean water, and in/under alpine snowpack.
* Radioresistant: resistant to high levels of ionizing radiation, most commonly ultraviolet radiation but also includes organisms capable of resisting nuclear radiation.
* Thermophile: An organism that can thrive at temperatures between 60-80 °C.
* Xerophile: An organism that can grow in extremely dry, desiccating conditions. This type is exemplified by the soil microbes of the Atacama Desert.

Extremophiles and astrobiology

Astrobiology is the field concerned with forming theories, such as panspermia, about the distribution, nature, and future of life in the universe. In it, microbial ecologists, astronomers, planetary scientists, geochemists, philosophers, and explorers cooperate to constructively guide the search for life on other planets. Astrobiologists are particularly interested in studying extremophiles, as many organisms of this type are capable of surviving in environments similar to those known to exist on other planets. For example, Mars may have regions in its deep subsurface permafrost that could harbor endolith communities. The subsurface water ocean of Jupiter's moon Europa may harbor life, especially at hypothesized hydrothermal vents at the ocean floor.

External links

* [https://inlportal.inl.gov/portal/server.pt?open=514&objID=2660&parentname=CommunityPage&parentid=0&mode=2&in_hi_userid=200&cached=true Extremophile Research]
* [http://www.nhm.ac.uk/zoology/extreme.html Eukaryotes in extreme environments]
* [http://www.daviddarling.info/encyclopedia/E/extremophile.html DaveDarling's Encyclopedia of Astrobiology, Astronomy, and Spaceflight]
* [http://extremophiles.org/index.html The International Society for Extremophiles]

References

*cite journal
author=Rossi M et al
title=Extremophiles 2002
journal=J Bacteriol.
year=2003
month=Jul
volume=185
issue=13
pages=3683–9
pmid=12813059
doi = 10.1128/JB.185.13.3683-3689.2003

*cite journal
title=Extremophilic microbes: Diversity and perspectives
author=Satyanarayana, T.
coauthors=Raghukumar, C.; Shivaji, S.
journal=Current Science
volume=89
issue=1
pages=78–90
year=2005
month=Jul
url=http://hdl.handle.net/2264/330


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Extremophile — Extrêmophile Les thermophiles, sont un type d organismes extremophiles se développant dans les sources chaudes comme le Grand Prismatic Spring, au Parc national de Yellowstone Un organisme est dit extrêmophile lorsque ses conditions de vie… …   Wikipédia en Français

  • Extrémophile — Extrêmophile Les thermophiles, sont un type d organismes extremophiles se développant dans les sources chaudes comme le Grand Prismatic Spring, au Parc national de Yellowstone Un organisme est dit extrêmophile lorsque ses conditions de vie… …   Wikipédia en Français

  • Extremophile — Als extremophil werden Organismen bezeichnet, die sich extremen Umweltbedingungen angepasst haben, die im Allgemeinen als lebensfeindlich betrachtet werden. Dabei handelt es sich meist um einzellige Mikroorganismen. Die Definition ‚extrem‘ ist… …   Deutsch Wikipedia

  • Extrêmophile — Les thermophiles, sont un type d organismes extrêmophiles se développant dans les sources chaudes comme le Grand Prismatic Spring, au Parc national de Yellowstone …   Wikipédia en Français

  • extremophile — noun Date: 1989 an organism that lives under extreme environmental conditions (as in a hot spring or ice cap) …   New Collegiate Dictionary

  • extremophile — An organism that requires an extreme enviroment in which to flourish examples are thermophiles and halophiles …   Dictionary of molecular biology

  • extremophile — noun An organism that lives under extreme conditions of temperature, salinity etc; commercially important as a source of enzymes that operate under similar conditions …   Wiktionary

  • extremophile — (ik.STREEM.uh.fyl) n. An organism whose natural habitat is an extreme environment. Example Citation: Those who think there could be life elsewhere in the solar system talk of the possibility of bacteria buried in the Martian icecaps, perhaps, or… …   New words

  • extremophile — n. organism (usually single celled) whose natural surroundings are in extreme environmental conditions (as in hot springs, ice cap, extreme temperatures or pressure) …   English contemporary dictionary

  • extremophile — [ɛks trɛməfʌɪl] noun Biology a microorganism that lives in extreme environmental conditions …   English new terms dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”