extremophile

Thermophiles, a type of extremophile, produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park

An extremophile (from Latin extremus meaning "extreme" and Greek philiā (φιλία) meaning "love") is an organism that thrives in and even may require physically or geochemically extreme conditions that are detrimental to the majority of life on Earth. In contrast, organisms from moderate temperature or neutral pH environments may be termed mesophiles or neutrophiles.

In the 1980s and 1990s, biologists found that microbial life has an amazing flexibility for surviving in extreme environments - niches that are extraordinarily hot, or cold, or dry, or under immense pressures - that would be completely inhospitable to complex organisms. Some scientists even concluded that life may have begun on Earth in hydrothermal vents far under the ocean's surface.^[1]

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; protostome animals 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 optimal growth at pH levels of 3 or below

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, a term that also includes organisms populating fissures, aquifers, and faults filled with groundwater in the deep subsurface

Halophile

An organism requiring at least 0.2M concentrations of salt (NaCl) for growth^[2]

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 or under alpine snowpack

Radioresistant

Organisms resistant to high levels of ionizing radiation, most commonly ultraviolet radiation, but also including organisms capable of resisting nuclear radiation

Thermophile

An organism that can thrive at temperatures between 60–80 °C

Thermoacidophile

Combination of thermophile and acidophile that prefer temperatures of 70–80 °C and pH between 2 and 3

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 constructively to 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.

References

1. ^ "Mars Exploration - Press kit" (PDF). NASA. June 2003. http://marsrovers.jpl.nasa.gov/newsroom/merlaunch.pdf. Retrieved 2009-07-14. 
2. ^ Cavicchioli, R. & Thomas, T. 2000. Extremophiles. In: J. Lederberg. (ed.) Encyclopedia of Microbiology, Second Edition, Vol. 2, pp. 317–337. Academic Press, San Diego.

This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (April 2009)

• Wilson, Z. E. and Brimble, M. A. (January 2009). "Molecules derived from the extremes of life". Nat. Prod. Rep. 26 (1): 44–71. doi:10.1039/b800164m. 
• Rossi M et al. (July 2003). "Extremophiles 2002". J Bacteriol. 185 (13): 3683–9. doi:10.1128/JB.185.13.3683-3689.2003. PMID 12813059. 
• Satyanarayana, T.; Raghukumar, C.; Shivaji, S. (July 2005). "Extremophilic microbes: Diversity and perspectives". Current Science 89 (1): 78–90. http://hdl.handle.net/2264/330. 

External links

Wikinews has related news: Bacteria thrive deep under sea floor

• Extremophile Research
• Eukaryotes in extreme environments
• The Research Center of Extremophiles
• DaveDarling's Encyclopedia of Astrobiology, Astronomy, and Spaceflight
• The International Society for Extremophiles

v • d • e Extremophiles Categories Acidophile · Alkaliphile · Capnophile · Endolith · Halophile · Hyperthermophile · Hypolith · Lipophile  · Lithoautotroph · Lithophile  · Metalotolerant  · Oligotroph · Osmophile · Piezophile · Polyextremophile · Psychrophile · Thermophile · Thermoacidophile · Xerophile Notable extremophiles Bacteria Chloroflexus aurantiacus · Deinococcus radiodurans · Deinococcus-Thermus · Snottite · Thermus aquaticus · Thermus thermophilus · Spirochaeta americana Archaea Pyrococcus furiosus · Strain 121 Animalia Paralvinella sulfincola · Pompeii worm · Tardigrada Related articles Abiogenic petroleum origin · Acidithiobacillales · Acidobacteria · Acidophiles in acid mine drainage  · Archaeoglobaceae · Berkeley Pit · Blood Falls · Crenarchaeota · Grylloblattidae · Halobacteria · Halobacterium · Helaeomyia petrolei · Hydrothermal vent · Methanopyrus · Movile Cave · Radioresistance · Radiotrophic fungus  · Taq polymerase  · Thermostability · Thermotogae