- Extremophile
An extremophile is an
organism that thrives in and may even requirephysic ally orgeochemical ly extreme conditions that are detrimental to the majority oflife onEarth .Most known extremophiles are
microbes . The domainArchaea contains renowned examples, but extremophiles are present in numerous and diversegene tic lineages of bothbacteria and archaeans. Furthermore, it is erroneous to use the term extremophile to encompass all archaeans, as some are mesophilic. Neither are all extremophiles unicellular;protostome s found in similar environments include thePompeii worm , the psychrophilicGrylloblattodea (insect s),Antarctic krill (acrustacean ) 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 optimumpH level at or below pH 3.
*Alkaliphile : An organism with optimal growth atpH 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 calledcryptoendoliths . 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 ofcarbon iscarbon dioxide and exergonic inorganicoxidation (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 ascopper ,cadmium ,arsenic , andzinc . 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 hydrostaticpressure . Common in the deep terrestrial subsurface, as well as inoceanic trench es.
*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 ofionizing 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 theAtacama Desert .Extremophiles and astrobiology
Astrobiology is the field concerned with forming theories, such aspanspermia , 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 harborendolith communities. The subsurface water ocean ofJupiter '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
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