Endolith


Endolith
Endolith lifeform found inside an Antarctic rock

An endolith is an organism (archaeum, bacterium, fungus, lichen, alga or amoeba) that lives inside rock, coral, animal shells, or in the pores between mineral grains of a rock. Many are extremophiles, living in places previously thought inhospitable to life. They are of particular interest to astrobiologists, who theorize that endolithic environments on Mars and other planets constitute potential refugia for extraterrestrial microbial communities.[citation needed]

Contents

Subdefinitions

The term "endolith", which defines an organism that colonizes the interior of any kind of rock, has been further classified into three subclasses:[1]

Chasmoendolith: colonizes fissures and cracks in the rock (chasm = cleft)
Cryptoendolith: colonizes structural cavities within porous rocks, including spaces produced and vacated by euendoliths (crypto = hidden)
Euendolith: penetrates actively into the interior of rocks forming tunnels that conform with the shape of its body, rock boring organism (eu = good, true)

Environment

Endoliths have been found in rock down to a depth of 3 kilometres (1.9 mi), though it is unknown if that is their limit (due to the cost involved in digging so deeply).[2][3] The main threat to their survival seems not to result from the pressure at such depth, but from the increased temperature. Judging from hyperthermophile organisms, the temperature limit is at about 120 °C (the recently discovered Strain 121 can reproduce at 121 °C), which limits the possible depth to 4-4.5 km below the continental crust, and 7 or 7.5 km below the ocean floor. Endolithic organisms have also been found in surface rocks in regions of low humidity (hypolith) and low temperature (psychrophile), including the Dry Valleys and permafrost of Antarctica,[4] the Alps[5] and the Rocky Mountains.[6][7]

Survival

Endoliths can survive by feeding on traces of iron, potassium, or sulfur. (See lithotroph.) Whether they metabolize these directly from the surrounding rock, or rather excrete an acid to dissolve them first, remains to be seen. The Ocean Drilling Program found microscopic trails in basalt from the Atlantic, Indian, and Pacific oceans that contain DNA.[8][9] Photosynthetic endoliths have also been discovered.

As water and nutrients are rather sparse in the environment of the endolith, they have a very slow reproduction cycle. Early data suggests that some only engage in cell division once every hundred years. Most of their energy is spent repairing cell damage caused by cosmic rays or racemization, and very little is available for reproduction or growth. It is thought that they weather long ice ages in this fashion, emerging when the temperature in the area warms.[3]

Slime

As most endoliths are autotrophs, they can generate organic compounds essential for their survival on their own from inorganic matter. Some endoliths have specialized in feeding on their autotroph relatives. The micro-biotope where these different endolithic species live together has been called a subsurface lithotrophic microbial ecosystem (SLiME).[10]

See also

References

External links

  • Endoliths General Collection — This collection of online resources such as news articles, web sites, and reference pages provides a comprehensive array of information about endoliths.
  • Endolith Advanced Collection — Compiled for professionals and advanced learners, this endolith collection includes online resources such as journal articles, academic reviews, and surveys.

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Look at other dictionaries:

  • Endolith — Endolithische Flechte der Gattung Verrucaria Als endolithisch wird die Lebensweise von Organismen im Inneren von Gesteinen bezeichnet (Endo : innen, im Inneren; lithos: der Stein). Die endolithische Lebensweise findet man nur bei Mikroorganismen …   Deutsch Wikipedia

  • endolith — A calcified body found in the pulp chamber of a tooth; may be composed of irregular dentin (true denticle) or due to ectopic calcification of pulp tissue (false denticle). SYN: denticle (1), pulp calcification …   Medical dictionary

  • Endolith — En|do|lith [auch ... lit] der; Gen. s u. en, Plur. e[n] (meist Plur.) <zu ↑endo... u. ↑...lith> niedere Pflanze (vor allem Flechten u. Blaualgen), deren ↑Thallus tief in Steine einwächst (Bot.) …   Das große Fremdwörterbuch

  • endolith — coloured design on chemically prepared slab of marble or ivory Stones and Rocks …   Phrontistery dictionary

  • endolith — /ˈɛndoʊlɪθ/ (say endohlith) noun a microorganism able to live under extreme conditions, found inside a rock or in the pores between grains of a mineral. –endolithic /ɛndoʊˈlɪθɪk/ (say endoh lithik), adjective …   Australian English dictionary

  • Lithotroph — A lithotroph is an organism that uses an inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation via aerobic or anaerobic respiration.[1] Known… …   Wikipedia

  • Lithoautotroph — A lithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. They may also be referred to as chemolithoautotrophs, a type of lithotrophs, reflecting their autotrophic metabolic pathways. Lithoautotrophs are… …   Wikipedia

  • 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… …   Wikipedia

  • Oligotroph — An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments. Oligotrophs are characterized by slow growth, low rates… …   Wikipedia

  • Carnivore — Carnivorism redirects here. For the diet, see No carbohydrate diet. For other uses, see Carnivore (disambiguation). Lions are voracious carnivores; they require up to seven kilograms (15 lbs) of meat per day. A major component of their diet is… …   Wikipedia


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