A thermophile is an organism—a type of

extremophile An extremophile (from Latin ' meaning "extreme" and Greek ' () meaning "love") is an organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temper ...

—that thrives at relatively high temperatures, between . Many thermophiles are

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

, though they can be

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

or fungi. Thermophilic

eubacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

are suggested to have been among the earliest bacteria. Thermophiles are found in various geothermally heated regions of the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, such as hot springs like those in

Yellowstone National Park Yellowstone National Park is an American national park located in the western United States, largely in the northwest corner of Wyoming and extending into Montana and Idaho. It was established by the 42nd U.S. Congress with the Yellowston ...

(see image) and

deep sea The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 metres (656 feet) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combin ...

hydrothermal vent A hydrothermal vent is a fissure on the seabed from which geothermally heated water discharges. They are commonly found near volcanically active places, areas where tectonic plates are moving apart at mid-ocean ridges, ocean basins, and hotspot ...

s, as well as decaying plant matter, such as

peat bogs A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg ...

and

compost Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical and biological properties. It is commonly prepared by decomposing plant, food waste, recycling organic materials and manure. The resulting m ...

. Thermophiles can survive at high temperatures, whereas other bacteria or archaea would be damaged and sometimes killed if exposed to the same temperatures. The

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

s in thermophiles function at high temperatures. Some of these enzymes are used in

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and physi ...

, for example the ''Taq'' polymerase used in PCR. "Thermophile" is derived from the el, θερμότητα (''thermotita''), meaning

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

, and el, φίλια (''philia''),

love Love encompasses a range of strong and positive emotional and mental states, from the most sublime virtue or good habit, the deepest Interpersonal relationship, interpersonal affection, to the simplest pleasure. An example of this range of ...

Classification

Thermophiles can be classified in various ways. One classification sorts these organisms according to their optimal growth temperatures: # Simple thermophiles: 50–64 °C (122-147.2 °F) # Extreme thermophiles 65–79 °C (149-174.2 °F) # Hyperthermophiles 80 °C and beyond, but not < 50 °C. (176+ °F) In a related classification, thermophiles are sorted as follows: # Facultative thermophiles (also called moderate thermophiles) can thrive at high temperatures, but also at lower temperatures (below ), whereas # Obligate thermophiles (also called extreme thermophiles) require such high temperatures for growth. #

Hyperthermophile A hyperthermophile is an organism that thrives in extremely hot environments—from 60 °C (140 °F) upwards. An optimal temperature for the existence of hyperthermophiles is often above 80 °C (176 °F). Hyperthermophiles are often within the doma ...

s are particularly extreme thermophiles for which the optimal temperatures are above . Thermophilic bacteria

Many of the hyperthermophilic Archaea require elemental

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

for growth. Some are anaerobes that use the sulfur instead of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

as an electron acceptor during cellular respiration (anaerobic). Some are

lithotroph Lithotrophs are a diverse group of organisms using an 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 aerobi ...

s that oxidize sulphur to create

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

as an energy source, thus requiring the microorganism to be adapted to very low pH (i.e., it is an

acidophile Acidophiles or acidophilic organisms are those that thrive under highly acidic conditions (usually at pH 5.0 or below). These organisms can be found in different branches of the tree of life, including Archaea, Bacteria,Becker, A.Types of Bacteria ...

as well as thermophile). These organisms are inhabitants of hot, sulfur-rich environments usually associated with

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called ...

, such as

hot springs A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by circ ...

geysers A geyser (, ) is a spring characterized by an intermittent discharge of water ejected turbulently and accompanied by steam. As a fairly rare phenomenon, the formation of geysers is due to particular hydrogeological conditions that exist only in ...

, and

fumaroles A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcani ...

. In these places, especially in Yellowstone National Park, zonation of microorganisms according to their temperature optima occurs. These organisms are often colored, due to the presence of

photosynthetic Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in c ...

pigments.

Thermophile versus mesophile

Thermophiles can be discriminated from mesophiles from genomic features. For example, the GC-content levels in the coding regions of some signature genes were consistently identified as correlated with the temperature range condition when the association analysis was applied to mesophilic and thermophilic organisms regardless of their phylogeny, oxygen requirement, salinity, or habitat conditions. = Fungal thermophiles = Fungi are the only group of organisms in the Eukarya kingdom that can survive at temperature ranges of 50–60 °C. Thermophilic fungi have been reported from a number of habitats, with most of them belonging to the fungal order

Sordariales The order Sordariales is one of the most diverse taxonomic groups within the Sordariomycetes (subdivision Pezizomycotina, division Ascomycota). Species in the order Sordariales have a broad range of ecological diversity, containing lignicolous, ...

. Thermophilic fungi have great biotechnological potential due to their ability to produce industrial-relevant thermostable enzymes, in particular for the degradation of plant biomass.

Gene transfer and genetic exchange

Sulfolobus solfataricus ''Saccharolobus solfataricus'' is a species of thermophilic archaeon. It was transferred from the genus ''Sulfolobus'' to the new genus ''Saccharolobus'' with the description of Saccharolobus caldissimus in 2018. It was first isolated and disco ...

'' and ''

Sulfolobus acidocaldarius ''Sulfolobus acidocaldarius'' is a thermoacidophilic archaeon that belongs to the phylum Thermoproteota. ''S. acidocaldarius'' was the first ''Sulfolobus'' species to be described, in 1972 by Thomas D. Brock and collaborators. This species was ...

'' are hyperthermophilic archaea. When these organisms are exposed to the DNA damaging agents UV irradiation, bleomycin or mitomycin C, species-specific cellular aggregation is induced. In ''S. acidocaldarius'', UV-induced cellular aggregation mediates chromosomal marker exchange with high frequency. Recombination rates exceed those of uninduced cultures by up to three orders of magnitude. Frols et al. and Ajon et al.(2011) hypothesized that cellular aggregation enhances species-specific DNA transfer between ''Sulfolobus'' cells in order to provide increased repair of damaged DNA by means of

homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...

. Van Wolferen et al., in discussing DNA exchange in the hyperthermophiles under extreme conditions, noted that DNA exchange likely plays a role in repair of DNA via homologous recombination. They suggested that this process is crucial under DNA damaging conditions such as high temperature. Also it has been suggested that DNA transfer in ''Sulfolobus'' may be a primitive form of sexual interaction similar to the more well-studied bacterial transformation systems that are associated with species-specific DNA transfer between cells leading to homologous recombinational repair of DNA damage ee_Transformation_(genetics).html" ;"title="Transformation_(genetics).html" ;"title="ee Transformation (genetics)">ee Transformation (genetics)">Transformation_(genetics).html" ;"title="ee Transformation (genetics)">ee Transformation (genetics)

References

External links

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How hot is too Hot? T-Limit Expedition
{{Extremophile Anaerobic digestion Biodegradation Biodegradable waste management Thermozoa Geysers Morocco articles missing geocoordinate data

Classification

Thermophile versus mesophile

Gene transfer and genetic exchange

See also

References

External links