Endolith

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Endolith

An endolith is an organism

Organism

In biology, an organism is any life thing . In at least some form, all organisms are capable of response to stimulus , reproduction, growth and developmental biology, and maintenance of homeostasis as a stable whole....
(archaeum, bacterium, fungus

Fungus

A fungus is a Eukaryote organism that is a member of the Kingdom Fungi . The fungi are a monophyletic group, also called the Eumycota , that is phylogeny distinct from the morphologically similar slime molds and water molds ....
, lichen

Lichen

Lichens are composite organisms consisting of a symbiosis association of a fungus with a Photosynthesis partner , usually either a green algae or Cyanobacteria ....
, alga or amoeba

Amoeba

Amoeba is a term used either to describe protists that move by crawling via pseudopods, or to refer to a genus that includes species that move by this mechanism....
) that lives inside rock

Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
, coral

Coral

Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....
, animal shells, or in the pore

Porosity

Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0?1, or as a percentage between 0?100%. The term is used in multiple fields including ceramics, metallurgy, materials, manufacturing, earth sciences and construction....
s between mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
grains of a rock. Many are extremophile

Extremophile

An extremophile is an organism that thrives in and may even require physically or geochemically extreme environment that are detrimental to the majority of life on Earth....
s; living in places previously thought inhospitable to life. They are of particular interest to astrobiologists

Astrobiology

Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. This interdisciplinary field encompasses the search for habitable environments in our Solar System and Planetary habitability outside our Solar System, the search for evidence of Abiogenesis, life on Mars and other bodies in our Solar Syst...
, who theorize that endolithic environments on Mars and other planets constitute potential refugia

Refugia

In biology a refugium is a location of an isolated or relict population of a once widespread species.This isolation can be due to climatic changes or human activities such as deforestation and over-hunting....
for extraterrestrial microbial communities.

>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 km (9,600 feet), though it is unknown if that is their limit (due to the cost involved in digging so deeply).

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Encyclopedia

An endolith is an organism

Organism

Fungus

Lichen

Lichens are composite organisms consisting of a symbiosis association of a fungus with a Photosynthesis partner , usually either a green algae or Cyanobacteria ....
, alga or amoeba

Amoeba

Amoeba is a term used either to describe protists that move by crawling via pseudopods, or to refer to a genus that includes species that move by this mechanism....
) that lives inside rock

Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
, coral

Coral

Corals are marine organisms from the class Anthozoa and exist as small sea anemone?like polyps, typically in colonies of many identical individuals....
, animal shells, or in the pore

Porosity

Mineral

Extremophile

Astrobiology

Refugia

Subdefinitions

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

- 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 km (9,600 feet), though it is unknown if that is their limit (due to the cost involved in digging so deeply). The main threat to their survival seems not to result from the pressure at such depth, but from the increased temperature. Judging from hyperthermophile

Hyperthermophile

A hyperthermophile is an organism that thrives in extremely hot environments? from 60 degrees C upwards. An optimal temperature for the existence of Hyperthermophiles are above 80?C ....
organisms, the temperature limit is at about 120°C

Celsius

Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death....
(the recently-discovered Strain 121

Strain 121

Strain 121 is a single-cell ed microbe, of the domain Archaea. First discovered off Puget Sound in a hydrothermal vent, it is a hyperthermophile, able to survive and reproduce at ....
can reproduce at 121°C), which limits the possible depth to 4-4.5 km below the continent

Continent

A continent is one of several large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents ? they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia ....
al crust, and 7 or 7.5 km below the ocean

Ocean

An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas....
floor. Endolithic organisms have also been found in surface rocks in regions of low humidity (hypolith

Hypolith

In Arctic and Antarctic ecology, a hypolith is a photosynthetic organism that livesunderneath rock in climate extreme deserts such as Cornwallis Island and Devon Island in the Canadian high Arctic....
) and low temperature (psychrophile

Psychrophile

Psychrophiles or Cryophiles are extremophile organisms that are capable of cell growth and biological reproduction in cold temperatures. They can be contrasted with thermophiles, which thrive at unusually hot temperatures....
), including the Dry Valleys and permafrost

Permafrost

In geology, permafrost or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material....
of Antarctica

Antarctica

Antarctica is Earth's southernmost continent, overlying the South Pole. It is situated in the Antarctica of the southern hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean....
.

Survival

Endoliths can survive by feeding on traces of iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
, potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
, or sulfur

Sulfur

Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant Valence non-metal....
. (See lithotroph

Lithotroph

A lithotroph is an organism that uses an inorganic substrate to obtain reducing equivalents for use in biosynthesis or energy conservation via aerobic or anaerobic respiration....
.) Whether they metabolize

Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
these directly from the surrounding rock, or rather excrete

Excretion

Excretion is the process of eliminating waste products of metabolism and other non-useful materials. It is an essential process in all forms of life....
an acid

Acid

An acid is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion Activity greater than in pure water, i.e....
to dissolve them first, remains to be seen. The Ocean Drilling Program

Ocean Drilling Program

The Ocean Drilling Program was an international cooperative effort to explore and study the composition and structure of the earth's ocean basins....
found microscopic trails in basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet....
from the Atlantic

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions; with a total area of about 106.4 million square kilometres . It covers approximately one-fifth of the Earth's surface....
, Indian

Indian Ocean

The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by Asia ; on the west by Africa; on the east by Indochina, the Sunda Islands, and Australia; and on the south by the Southern Ocean ....
, and Pacific ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. Its name is derived from the Latin name Mare Pacificum, "peaceful sea", bestowed upon it by the Portugal explorer Ferdinand Magellan....
s that contain DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetics instructions used in the development and functioning of all known living organisms and some viruses....
. 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

Cell division

Cell division is a process by which a cell , called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle....
once every hundred years. Most of their energy is spent repairing cell damage caused by cosmic ray

Cosmic ray

Cosmic rays are energetic particles originating from space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, about 9% are helium nuclei and about 1% are electrons ....
s or racemization

Racemization

In chemistry racemization refers to partial conversion of one enantiomer into another....
, and very little is available for reproduction or growth. It is thought that they weather long ice age

Ice age

The general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers....
s in this fashion, emerging when the temperature in the area warms.

Slime

As most endoliths are autotroph

Autotroph

An autotroph is an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions....
s, they can generate organic compounds essential for their survival on their own from inorganic matter. Inevitably, some endoliths have specialized in feeding on their autotroph relatives. The micro-biotope

Biotope

Biotope is an area of uniform environmental conditions providing a living place for a specific assemblage of flora and fauna . Biotope is almost synonymous with the term habitat , but while the subject of a habitat is a species or a population, the subject of a biotope is a biocoenosis....
where these different endolithic species live together is called SLiME (Subsurface Lithotrophic Microbial Ecosystem).

External links

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

Endolith

Subdefinitions

Environment

Survival

Slime

See also

External links