A
thermophile is an organism — a type of
extremophileAn extremophile 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...
— that thrives at relatively high temperatures, between 45 and 80 °C (113 and 176 °F). Many thermophiles are
archaeaThe Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . They have no cell nucleus or any other organelles within their cells...
.
Thermophiles are found in various geothermally heated regions of the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
such as hot springs like those in
Yellowstone National ParkYellowstone National Park, established by the U.S. Congress as a national park on March 1, 1872 , is located primarily in the U.S. state of Wyoming, though it also extends into Montana and Idaho. The park was the first of its kind, and is known for its wildlife and its many geothermal features,...
(see image) and
deep seaThe deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline, at a depth of 1000 fathoms or more. Little or no light penetrates this area of the ocean, and most of its organisms rely on falling organic matter produced in the photic zone for subsistence...
hydrothermal ventA hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots....
s, as well as decaying plant matter such as peat bogs and compost.
As a prerequisite for their survival, thermophiles contain
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s that can function at high temperature.
A
thermophile is an organism — a type of
extremophileAn extremophile 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...
— that thrives at relatively high temperatures, between 45 and 80 °C (113 and 176 °F). Many thermophiles are
archaeaThe Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon . They have no cell nucleus or any other organelles within their cells...
.
Thermophiles are found in various geothermally heated regions of the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
such as hot springs like those in
Yellowstone National ParkYellowstone National Park, established by the U.S. Congress as a national park on March 1, 1872 , is located primarily in the U.S. state of Wyoming, though it also extends into Montana and Idaho. The park was the first of its kind, and is known for its wildlife and its many geothermal features,...
(see image) and
deep seaThe deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline, at a depth of 1000 fathoms or more. Little or no light penetrates this area of the ocean, and most of its organisms rely on falling organic matter produced in the photic zone for subsistence...
hydrothermal ventA hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots....
s, as well as decaying plant matter such as peat bogs and compost.
As a prerequisite for their survival, thermophiles contain
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s that can function at high temperature. Some of these enzymes are used in
molecular biologyMolecular biology is the study of biology at a molecular level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...
(for example, heat-stable
DNA polymeraseA DNA polymerase is an enzyme that catalyzes the polymerization of deoxyribonucleotides into a DNA strand. DNA polymerases are best-known for their role in DNA replication, in which the polymerase "reads" an intact DNA strand as a template and uses it to synthesize the new strand...
s for
PCRIn molecular biology, the polymerase chain reaction is a technique to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence...
), and in washing agents.
Thermophiles are classified into obligate and facultative thermophiles: Obligate thermophiles (also called
extreme thermophiles) require such high temperatures for growth, whereas facultative thermophiles (also called
moderate thermophiles) can thrive at high temperatures but also at lower temperatures (below 50 °C).
HyperthermophileA hyperthermophile is an organism that thrives in extremely hot environments— from 60 degrees C upwards. An optimal temperature for the existence of Hyperthermophiles is above 80°C . Hyperthermophiles are a subset of extremophiles, micro-organisms within the domain Archaea, although some bacteria...
s are particularly extreme thermophiles for which the optimal temperatures are above 80 °C.
Thermophile is descended from the (thermotita), meaning heat, and (philia), love.
Extreme Thermophiles
Thermophiles, meaning heat-loving organisms, are organisms with an optimum growth temperature of 50 °C or more, a maximum of up to 70 °C or more, and a minimum of about 40 degrees C, but these are only approximate. Some extreme thermophiles (
hyperthermophileA hyperthermophile is an organism that thrives in extremely hot environments— from 60 degrees C upwards. An optimal temperature for the existence of Hyperthermophiles is above 80°C . Hyperthermophiles are a subset of extremophiles, micro-organisms within the domain Archaea, although some bacteria...
s) require a very high temperature (80 °C to 105 °C) for growth. Their membranes and proteins are unusually stable at these extremely high temperatures. Thus many important biotechnological processes utilize thermophilic
enzymeEnzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, called the products. Almost all processes in a biological cell need enzymes to occur at...
s because of their ability to withstand intense heat.
Many of the hyperthermophiles Archea require elemental
sulfurSulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
for growth. Some are anaerobes that use the sulfur instead of
oxygenOxygen Oxygen Oxygen (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter) is the element with atomic number 8 and represented by the symbol O...
as an
electron acceptorAn electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process....
during
cellular respirationCellular respiration is one of the key ways a cell gains useful energy. It is the set of the metabolic reactions and processes that take place in organisms' cells to convert biochemical energy from nutrients into adenosine triphosphate , and then release waste products...
. Some are
lithotrophA 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. Known lithotrophs are exclusively microbes or plants; No known macrofauna possesses the ability to utilize inorganic...
s that oxidize sulfur to
sulfuric acidSulfuric acid, , is a strong mineral acid. It is soluble in water at all concentrations. Sulfuric acid has many applications, and is one of the top products of the chemical industry. World production in 2001 was 165 million tonnes, with an approximate value of US$8 billion...
as an energy source, thus requiring the microorganism to be adapted to very low
pHpH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations...
(i.e., it is an
acidophileAcidophilic organisms are those that thrive under highly acidic conditions . These organisms can be found in different branches of the tree of life, including Archaea, Bacteria, and Eukaryotes...
as well as thermophile). These organisms are inhabitants of hot, sulfur-rich environments usually associated with volcanism, such as
hot springsHot Springs may refer to:* Hot Springs, Arkansas*Hot Springs, California**Hot Springs, Lassen County, California**Hot Springs, Modoc County, California**Hot Springs, Plumas County, California* Hot Springs, Montana* Hot Springs, North Carolina...
, geysers, and fumaroles. In these places, especially in Yellowstone National Park, we find a zonation of microorganisms according to their temperature optima. Often these organisms are coloured, due to the presence of photosynthetic pigments.
Genomic and Proteomic Features of Thermophiles
The
genomeIn modern molecular biology the genome refers to all of its hereditary information encoded in DNA .The genome includes both the genes and the non-coding sequences of the DNA. The term was adapted in 1920 by Hans Winkler, Professor of Botany at the University of Hamburg, Germany...
and
proteomeThe proteome is the entire complement of proteins expressed by a genome, cell, tissue or organism. More specifically, it is the set of expressed proteins at a given time under defined conditions. The term is a portmanteau of proteins and genome....
composition of thermophiles are characterized by overrepresentation of
purineA purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....
bases in protein coding sequences, higher
GC-contentGC-content , in molecular biology, is the percentage of nitrogenous bases on a DNA molecule which are either guanine or cytosine . This may refer to a specific fragment of DNA or RNA, or that of the whole genome...
of the structural
RNARibonucleic acid is a biologically important type of molecule that consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate...
s, distinct synonymous
codonThe genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells. A more precise term for the concept might be "genetic cipher". The code defines a mapping between tri-nucleotide sequences, called codons, and amino acids...
usage, enhanced usage of positively charged residues and
aromaticIn organic chemistry, the structures of some rings of atoms are unexpectedly stable. Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone...
residueAmino acids are molecules containing an amine group, a carboxylic acid group and one of the twenty R-groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H
2NCHRCOOH, where R is an organic substituent...
s, decrease in polar uncharged residues in the encoded protein.
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