An endolith is an organism (archaeon, bacterium, fungus, lichen, algae 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 long imagined 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.[1][2]

Endolith lifeform found inside an Antarctic rock


The term "endolith", which defines an organism that colonizes the interior of any kind of rock, has been further classified into three subclasses:[3]

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


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 deep).[4][5] 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 (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,[6] the Alps,[7] and the Rocky Mountains.[8][9]


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.[10][11] Photosynthetic endoliths have also been discovered.[12]

As water and nutrients are rather sparse in the environment of the endolith, they have a very slow reproduction cycle. Early data suggest some only engage in cell division once every hundred years. In August 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years.[13] 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.[5]


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).[14]

Endolithic fungi and algae in marine ecosystems

Only limited research has been done concerning the distribution of marine endolithic fungi and its diversity even though there is a probability that endolithic fungi could perhaps play an important role in the health of coral reefs.

Endolithic fungi have been discovered in shells as early as the year 1889 by Edouard Bornet and Charles Flahault. These two French phycologists specifically provided descriptions for two fungi: Ostracoblabe implexis and Lithopythium gangliiforme. Discovery of endolithic fungi, such as Dodgella priscus and Conchyliastrum, has also been made in the beach sand of Australia by George Zembrowski. Findings have also been made in coral reefs and have been found to be, at times, beneficial to their coral hosts.[15]

In the wake of worldwide coral bleaching, studies have suggested that the endolithic algae located in the skeleton of the coral may be aiding the survival of coral species by providing an alternative source of energy. Although the role that endolithic Fungi play is important in coral reefs, it is often overlooked because much research is focused on the effects of coral bleaching as well as the relationships between coelenterate and endosymbiotic symbiodinia.[16]

According to a study done by Astrid Gunther endoliths were also found in the island of Cozumel (Mexico). The endoliths found there not only included algae and fungi but also included cyanobacteria, sponges as well as many other microborers.[17]

Endolithic parasitism

Until the 1990s phototrophic endoliths were thought as somewhat benign but since then evidence has surfaced that phototrophic endoliths (primarily cyanobacteria) have infested 50 to 80% of midshore populations of the mussel species Perna perna located in South Africa.The infestation of Phototrophic endoliths resulted in lethal and sub-lethal effects such as the decrease in strength of the mussel shells. Although the rate of thickening of the shells were faster in more infested areas it is not rapid enough to combat the degradation of the mussel shells.[18]

Endolithic fungi and the mass extinction of Cretaceous dinosaurs

Evidence of endolithic fungi were discovered within dinosaur eggshell found in central China. They were characterized as being “needle-like, ribbon-like, and silk-like."[19]

Fungus is seldom fossilized and even when it is preserved it can be difficult to distinguish endolithic hyphae from endolithic cyanobacteria and algae. Endolithic microbes can, however, be distinguished based on their distribution, ecology, and morphology. According to a 2008 study, the endolithic fungi that formed on the eggshells would have resulted in the abnormal incubation of the eggs and may have contributed to the mass extinction of these dinosaurs. It may also have led to the preservation of dinosaur eggs, including some that contained embryos.[19]

See also


  1. ^ Wierzchos, J.; Camara, B.; De Los Rios, A.; Davila, A. F.; Sanchaz Almazo, M.; Artieda, O.; Wierzchos, K.; Gomez-Silva, B.; McKay, C.; Ascaso, C. (2011). "Microbial colonization of Ca-sulfate crusts in the hyperarid core of the Atacama Desert: Implications for the search for life on Mars". Geobiology. 9 (1): 44–60. doi:10.1111/j.1472-4669.2010.00254.x. PMID 20726901.
  2. ^ Chang, Kenneth (12 September 2016). "Visions of Life on Mars in Earth's Depths". The New York Times. Retrieved 12 September 2016.
  3. ^ Stjepko Golubic; E.Imre Friedmann; Jürgen Schneider (June 1981). "The lithobiotic ecological niche, with special reference to microorganisms". Journal of Sedimentary Research. 51 (2): 475–478. Archived from the original on 30 December 2010.
  4. ^ Schultz, Steven (13 December 1999). "Two miles underground". Princeton Weekly Bulletin. Archived from the original on 13 January 2016. — Gold mines present "ideal environment" for geologists studying subsurface microbes
  5. ^ a b Looking for life in all the wrong places — research on cryptoendoliths Discover, May 1997 by Will Hively
  6. ^ Microbial Diversity of Cryptoendolithic Communities from the McMurdo Dry Valleys, Antarctica
  7. ^ Horath, Thomas; Bachofen, Reinhard (August 2009). "Molecular Characterization of an Endolithic Microbial Community in Dolomite Rock in the Central Alps (Switzerland)". Microbial Ecology. 58 (2): 290–306. doi:10.1007/s00248-008-9483-7. PMID 19172216.
  8. ^ Walker JJ, Spear JR, Pace NR (2005) Geobiology of a microbial endolithic community in the Yellowstone geothermal environment. Nature 434:1011–1014
  9. ^ Walker JJ, Pace NR (2007) Phylogenetic composition of Rocky Mountain endolithic microbial ecosystems. Appl Environ Microbiol 73:3497–3504
  10. ^ Mullen, Leslie. "Glass Munchers Under the Sea". NASA Astrobiology Institute. Archived from the original on 20 February 2013.
  11. ^ Lysnes, Kristine; Torsvik, Terje; Thorseth, Ingunn H.; Pedersen, Rolf B. (2004). "Microbial Populations in Ocean Floor Basalt: Results from ODP Leg 187" (PDF). Proc ODP Sci Results. 187: 1–27.
  12. ^ Wierzchos, J., Ascaso, C., and McKay., C. P.(2006). Astrobiology, 6(3): 415-422. doi:10.1089/ast.2006.6.415.
  13. ^ Yirka, Bob (29 August 2013). "Soil beneath ocean found to harbor long lived bacteria, fungi and viruses". Phys.org. Archived from the original on 29 October 2015.
  14. ^ "Frequently Requested Information about the SLiME Hypothesis". Archived from the original on 30 September 2006.
  15. ^ Golubic, Stjepko, Gudrun Radtke, and Therese Le Campion-Alsumard. "Endolithic fungi in marine ecosystems." Trends in Microbiology 13.5 (2005): 229-235.
  16. ^ Fine, M., and Y. Loya. "Endolithic Algae: An Alternative Source of Photoassimilates during Coral Bleaching." Proceedings of the Royal Society B: Biological Sciences 269.1497 (2002): 1205-210. Web.
  17. ^ Günther, Dipl Biol Astrid. "Distribution and bathymetric zonation of shell-boring endoliths in recent reef and shelf environments: Cozumel, Yucatan (Mexico)." Facies 22.1 (1990): 233-261.
  18. ^ Kaehler, S., and C. D. McQuaid. "Lethal and sub-lethal effects of phototrophic endoliths attacking the shell of the intertidal mussel Perna perna." Marine Biology 135.3 (1999): 497-503.
  19. ^ a b Gong, YiMing, Ran Xu, and Bi Hu. "Endolithic fungi: A possible killer for the mass extinction of Cretaceous dinosaurs." Science in China Series D: Earth Sciences 51.6 (2008): 801-807.

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.
Abiotic component

In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them underpin all biology.

Abiotic components include physical conditions and non-living resources that affect living organisms in terms of growth, maintenance, and reproduction. Resources are distinguished as substances or objects in the environment required by one organism and consumed or otherwise made unavailable for use by other organisms.

Component degradation of a substance occurs by chemical or physical processes, e.g. hydrolysis. All non-living components of an ecosystem, such as atmospheric conditions and water resources, are called abiotic components.


Bacterivores are free-living, generally heterotrophic organisms, exclusively microscopic, which obtain energy and nutrients primarily or entirely from the consumption of bacteria. Many species of amoeba are bacterivores, as well as other types of protozoans. Commonly, all species of bacteria will be prey, but spores of some species, such as Clostridium perfringens, will never be prey, because of their cellular attributes.


A copiotroph is an organism found in environments rich in nutrients, particularly carbon. They are the opposite to oligotrophs, which survive in much lower carbon concentrations.

Copiotrophic organisms tend to grow in high organic substrate conditions. For example, copiotrophic organisms grow in Sewage lagoons. They grow in organic substrate conditions up to 100x higher than oligotrophs.


Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and development. While the terms decomposer and detritivore are often interchangeably used, detritivores must ingest and digest dead matter via internal processes while decomposers can directly absorb nutrients through chemical and biological processes hence breaking down matter without ingesting it. Thus, invertebrates such as earthworms, woodlice, and sea cucumbers are technically detritivores, not decomposers, since they must ingest nutrients and are unable to absorb them externally.


A denticle is any small tooth-like or bristle-like structure. "Denticle" may refer to:

Denticle (tooth feature), serrations on the teeth of dinosaurs, lizards, sharks, and mammals

Dermal denticles or placoid scales, in cartilaginous fishes

Pulp stone or endolith, a calcified mass in the pulp of a tooth

Dominance (ecology)

Ecological dominance is the degree to which a taxon is more numerous than its competitors in an ecological community, or makes up more of the biomass.

Most ecological communities are defined by their dominant species.

In many examples of wet woodland in western Europe, the dominant tree is alder (Alnus glutinosa).

In temperate bogs, the dominant vegetation is usually species of Sphagnum moss.

Tidal swamps in the tropics are usually dominated by species of mangrove (Rhizophoraceae)

Some sea floor communities are dominated by brittle stars.

Exposed rocky shorelines are dominated by sessile organisms such as barnacles and limpets.

Ecological threshold

Ecological threshold is the point at which a relatively small change or disturbance in external conditions causes a rapid change in an ecosystem. When an ecological threshold has been passed, the ecosystem may no longer be able to return to its state by means of its inherent resilience . Crossing an ecological threshold often leads to rapid change of ecosystem health. Ecological threshold represent a non-linearity of the responses in ecological or biological systems to pressures caused by human activities or natural processes.Critical load, tipping point and regime shift are examples of other closely related terms.

Feeding frenzy

In ecology, a feeding frenzy occurs when predators are overwhelmed by the amount of prey available. For example, a large school of fish can cause nearby sharks, such as the lemon shark, to enter into a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each other or anything else within biting range. Another functional explanation for feeding frenzy is competition amongst predators. This term is most often used when referring to sharks or piranhas. It has also been used as a term within journalism.


A lithoautotroph or chemolithoautotroph is a microbe which derives energy from reduced compounds of mineral origin. Lithoautotrophs are a type of lithotrophs with autotrophic metabolic pathways. Lithoautotrophs are exclusively microbes; macrofauna do not possess the capability to use mineral sources of energy. Most lithoautotrophs belong to the domain Bacteria, while some belong to the domain Archaea. For lithoautotrophic bacteria, only inorganic molecules can be used as energy sources. The term "Lithotroph" is from Greek lithos (λίθος) meaning "rock" and trōphos (τροφοσ) meaning "consumer"; literally, it may be read "eaters of rock". Many lithoautotrophs are extremophiles, but this is not universally so.

Lithoautotrophs are extremely specific in using their energy source. Thus, despite the diversity in using inorganic molecules in order to obtain energy that lithoautotrophs exhibit as a group, one particular lithoautotroph would use only one type of inorganic molecule to get its energy.


Lithotrophs are a diverse group of organisms using inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic or anaerobic respiration. Known chemolithotrophs are exclusively microorganisms; no known macrofauna possesses the ability to use inorganic compounds as energy sources. Macrofauna and lithotrophs can form symbiotic relationships, in which case the lithotrophs are called "prokaryotic symbionts". An example of this is chemolithotrophic bacteria in giant tube worms or plastids, which are organelles within plant cells that may have evolved from photolithotrophic cyanobacteria-like organisms. Lithotrophs belong to either the domain Bacteria or the domain Archaea. The term "lithotroph" was created from the Greek terms 'lithos' (rock) and 'troph' (consumer), meaning "eaters of rock". Many but not all lithoautotrophs are extremophiles.

Different from a lithotroph is an organotroph, an organism which obtains its reducing agents from the catabolism of organic compounds.

Mesotrophic soil

Mesotrophic soils are soils with a moderate inherent fertility. An indicator of soil fertility is its base status, which is expressed as a ratio relating the major nutrient cations (calcium, magnesium, potassium and sodium) found there to the soil's clay percentage. This is commonly expressed in hundredths of a mole of cations per kilogram of clay, i.e. cmol (+) kg−1 clay.


Microecosystems can exist in locations which are precisely defined by critical environmental factors within small or tiny spaces.

Such factors may include temperature, pH, chemical milieu, nutrient supply, presence of symbionts or solid substrates, gaseous atmosphere (aerobic or anaerobic) etc.


A mycotroph is a plant that gets all or part of its carbon, water, or nutrient supply through symbiotic association with fungi. The term can refer to plants that engage in either of two distinct symbioses with fungi:

Many mycotrophs have a mutualistic association with fungi in any of several forms of mycorrhiza. The majority of plant species are mycotrophic in this sense. Examples include Burmanniaceae.

Some mycotrophs are parasitic upon fungi in an association known as myco-heterotrophy.


An organotroph is an organism that obtains hydrogen or electrons from organic substrates. This term is used in microbiology to classify and describe organisms based on how they obtain electrons for their respiration processes. Some organotrophs such as animals and many bacteria, are also heterotrophs. Organotrophs can be either anaerobic or aerobic.

Antonym: Lithotroph, Adjective: Organotrophic.


Overpopulation occurs when a species' population exceeds the carrying capacity of its ecological niche. It can result from an increase in births (fertility rate), a decline in the mortality rate, an increase in immigration, or an unsustainable biome and depletion of resources. When overpopulation occurs, individuals limit available resources to survive.

The change in number of individuals per unit area in a given locality is an important variable that has a significant impact on the entire ecosystem.


A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton.

Population cycle

A population cycle in zoology is a phenomenon where populations rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems. There are a number of factors which influence population change such as availability of food, predators, diseases and climate.

Recruitment (biology)

In biology, especially marine biology, recruitment occurs when a juvenile organism joins a population, whether by birth or immigration, usually at a stage whereby the organisms are settled and able to be detected by an observer.There are two types of recruitment: closed and open.In the study of fisheries, recruitment is "the number of fish surviving to enter the fishery or to some life history stage such as settlement or maturity".

Relative abundance distribution

In the field of ecology, the relative abundance distribution (RAD) or species abundance distribution describes the relationship between the number of species observed in a field study as a function of their observed abundance. The graphs obtained in this manner are typically fitted to a Zipf–Mandelbrot law, the exponent of which serves as an index of biodiversity in the ecosystem under study.

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