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 domain
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 ...
, although some
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 ...
are also able to tolerate extreme temperatures. Some of these bacteria are able to live at temperatures greater than 100 °C, deep in the ocean where
high pressures increase the boiling point of water. Many hyperthermophiles are also able to withstand other environmental extremes, such as high acidity or high radiation levels. Hyperthermophiles are a subset 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 ...
s. Their existence may support the possibility of
extraterrestrial life
Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might ...
, showing that
life
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...
can thrive in environmental extremes.
History
Hyperthermophiles isolated from hot springs 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 ...
were first reported by
Thomas D. Brock
Thomas Dale Brock (September 10, 1926 – April 4, 2021) was an American microbiologist known for his discovery of hyperthermophiles living in Geothermal areas of Yellowstone, hot springs at Yellowstone National Park. In the late 1960s, Brock di ...
in 1965. Since then, more than 70 species have been established. The most extreme hyperthermophiles live on the
superheated
A superheater is a device used to convert saturated steam or wet steam into superheated steam or dry steam. Superheated steam is used in steam turbines for electricity generation, steam engines, and in processes such as steam reforming. There are ...
walls of deep-sea
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, requiring temperatures of at least 90 °C for survival.
An extraordinary heat-tolerant hyperthermophile is ''
Strain 121'',
[Microbe from depths takes life to hottest known limit](_blank)
/ref> which has been able to double its population during 24 hours in an autoclave
An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilizat ...
at 121 °C (hence its name). The current record growth temperature is 122 °C, for '' Methanopyrus kandleri
In taxonomy, ''Methanopyrus'' is a genus of the Methanopyraceae.
''Methanopyrus'' is a genus of methanogen, with a single described species, ''M. kandleri''. It is a rod-shaped hyperthermophile, discovered on the wall of a black smoker from the ...
''.
Although no hyperthermophile has shown to thrive at temperatures >122 °C, their existence is possible. Strain 121 survives 130 °C for two hours, but was not able to reproduce until it had been transferred into a fresh growth medium, at a relatively cooler 103 °C.
Research
Early research into hyperthermophiles speculated that their genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ge ...
could be characterized by high guanine-cytosine content
In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out ...
; however, recent studies show that "there is no obvious correlation between the GC content of the genome and the optimal environmental growth temperature of the organism."[High guanine-cytosine content is not an adaptation to high temperature: a comparative analysis amongst prokaryotes](_blank)
/ref>
The protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
molecules in the hyperthermophiles exhibit hyperthermostability—that is, they can maintain structural stability (and therefore function) at high temperatures. Such proteins are homologous to their functional analogs in organisms that thrive at lower temperatures but have evolved to exhibit optimal function at much greater temperatures. Most of the low-temperature homologs of the hyperthermostable proteins would be denatured above 60 °C. Such hyperthermostable proteins are often commercially important, as chemical reactions proceed faster at high temperatures.
Specific hyperthermophiles
Archaea
* Strain 121, an archaeon
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 Archaebact ...
living at 121 °C in the Pacific Ocean.
* ''Pyrolobus fumarii
''Pyrolobus fumarii'' (literally the "firelobe of the chimney") is a species of archaea known for its ability to live at extremely high temperatures that kill most organisms.Joseph E. Armstrong. 2014. How the Earth Turned Green: A Brief 3.8-Billio ...
'', an archaeon
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 Archaebact ...
living at 113 °C in Atlantic hydrothermal vents.
* ''Pyrococcus furiosus
''Pyrococcus furiosus'' is a heterotrophic, strictly anaerobic, extremophilic, model species of archaea. It is classified as a hyperthermophile because it thrives best under extremely high temperatures, and is notable for having an optimum growt ...
'', an archaeon
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 Archaebact ...
which thrives at 100 °C, first discovered in Italy near a volcanic vent.
* ''Archaeoglobus
''Archaeoglobus'' is a genus of the phylum Euryarchaeota. ''Archaeoglobus'' can be found in high-temperature oil fields where they may contribute to oil field souring.
Metabolism
''Archaeoglobus'' grow anaerobically at extremely high temperat ...
fulgidus''
* ''Methanococcus jannaschii
''Methanocaldococcus jannaschii'' (formerly ''Methanococcus jannaschii'') is a thermophilic methanogenic archaean in the class Methanococci. It was the first archaeon to have its complete genome sequenced. The sequencing identified many genes un ...
''
* ''Aeropyrum pernix
''Aeropyrum pernix'' is a species of extremophile archaea in the archaeal phylum Thermoproteota. It is an obligatorily thermophilic species. The first specimens were isolated from sediments in the sea off the coast of Japan.
Discovery
''Aero ...
''
* ''Sulfolobus
''Sulfolobus'' is a genus of microorganism in the family Sulfolobaceae. It belongs to the archaea domain.
''Sulfolobus'' species grow in volcanic springs with optimal growth occurring at pH 2-3 and temperatures of 75-80 °C, making them ...
''
* ''Methanopyrus
In taxonomy, ''Methanopyrus'' is a genus of the Methanopyraceae.
''Methanopyrus'' is a genus of methanogen, with a single described species, ''M. kandleri''. It is a rod-shaped hyperthermophile, discovered on the wall of a black smoker from the ...
kandleri'' strain 116, an archaeon
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 Archaebact ...
in 80–122 °C in a Central Indian Ridge
The Central Indian Ridge (CIR) is a north–south-trending mid-ocean ridge in the western Indian Ocean.
Geological setting
The morphology of the CIR is characteristic of slow to intermediate ridges. The axial valley is 500–1000 m deep; ...
.
Gram-negative Bacteria
* ''Aquifex aeolicus
"''Aquifex aeolicus''" is a chemolithoautotrophic, Gram-negative, motile, hyperthermophilic bacterium. "''A. aeolicus"'' is generally rod-shaped with an approximate length of 2.0-6.0μm and a diameter of 0.4-0.5μm. "''A. aeolicus''" is neither v ...
''
* ''Geothermobacterium ferrireducens'', which thrives in 65–100 °C in Obsidian Pool, Yellowstone National Park.
* ''Thermotoga
''Thermotoga'' is a genus of the phylum ''Thermotogota''. Members of ''Thermotoga'' are hyperthermophilic bacteria whose cell is wrapped in a unique sheath-like outer membrane, called a "toga".
The members of the phylum stain Gram-negative as th ...
'', especially ''Thermotoga maritima
''Thermotoga maritima'' is a hyperthermophilic, anaerobic organism that is a member of the order Thermotogales. ''T. maritima'' is well known for its ability to produce hydrogen (clean energy) and it is the only fermentative bacterium that has be ...
''
See also
* Mesophile
A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37°C. The term is mainly applied to microorganisms. Organi ...
* Psychrophile
Psychrophiles or cryophiles (adj. ''psychrophilic'' or ''cryophilic'') are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from to . They have an optimal growth temperature at . They are found in ...
* Thermophile
A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...
* Unique properties of hyperthermophilic archaea
This article discusses the Unique properties of hyperthermophilic archaea. Hyperthermophiles are organisms that can live at temperatures ranging between 70 and 125 °C.Vieille, C. & Zeikus, G. J. "Hyperthermophilic Enzymes: Sources, Uses, and ...
References
Further reading
How hot is too Hot? T-Limit Expedition
{{Extremophile
Thermophiles
Geysers