Hipertermófilo: Diferenzas entre revisións

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Hyperthermophiles were first discovered by [[Thomas D. Brock]] in 1965, in hot springs in [[Yellowstone National Park]], [[Wyoming]].<ref>Joseph Seckbach, et al.: Polyextremophiles - life under multiple forms of stress. Springer, Dordrecht 2013, ISBN 978-94-007-6487-3,preface; [http://books.google.at/books?id=vRGvZmALC3YC&pg=PT3&dq=thomas+brock+1965+thermophiles+polyextremophiles&hl=en&sa=X&ei=F3z8Us3lBMOShQecwIGIDw&redir_esc=y#v=onepage&q=thomas%20brock%201965%20thermophiles%20polyextremophiles&f=false @google books] </ref><ref> [http://www.genetics.org/content/146/4/1207.full.pdf The Value of Basic Research: Discovery of 117termus aquaticus and Other Extreme Thermophiles]</ref> Since then, more than 70 species have been discovered.<ref>[http://www.dlr.de/me/Portaldata/25/Resources/dokumente/publikationen/P2_11.pdf Hyperthermophilic Microorganisms]</ref> The most hardy hyperthermophiles yet discovered live on the [[superheating|superheated]] walls of deep-sea [[hydrothermal vent]]s, requiring temperatures of at least 90&nbsp;°C for survival.

An extraordinary heat-tolerant hyperthermophile is the recently discovered ''[[Strain 121]]''<ref name="astrobio">[http://www.astrobiology.com/news/viewpr.html?pid=12337 Microbe from depths takes life to hottest known limit]</ref> which has been able to double its population during 24 hours in an [[autoclave]] at 121&nbsp;°C (hence its name); the current record growth temperature is 122&nbsp;°C, for ''[[Methanopyrus| Methanopyrus kandleri]]''.

Although no hyperthermophile has yet been discovered living at temperatures above 122&nbsp;°C, their existence is very possible (Strain 121 survived being heated to 130&nbsp;°C for two hours, but was [[bacteriostatic agent|not able to reproduce]] until it had been transferred into a fresh growth medium, at a relatively cooler 103&nbsp;°C). However, it is thought unlikely that microbes could survive at temperatures above 150&nbsp;°C, as the cohesion of [[DNA]] and other vital molecules begins to break down at this point.

 

Early research into hyperthermophiles speculated that their [[genome]] could be characterized by high [[GC-content|guanine-cytosine content]]; 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."<ref name="pubmed">[http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1088632 High guanine-cytosine content is not an adaptation to high temperature: a comparative analysis amongst prokaryotes<!-- Bot generated title -->]</ref><ref>{{cite journal |author=Zheng H, Wu H |title=Gene-centric association analysis for the correlation between the guanine-cytosine content levels and temperature range conditions of prokaryotic species |journal=BMC Bioinformatics |volume=11 |pages=S7 |date=December 2010 |doi=10.1186/1471-2105-11-S11-S7 |pmc=3024870 |pmid=21172057}}</ref>

 

The [[protein]] molecules in the hyperthermophiles exhibit hyperthermostability—that is, they can maintain structural stability (and therefore function) at high temperatures. Such proteins are [[homology (biology)|homologous]] to their functional analogues in organisms which thrive at lower temperatures, but have evolved to exhibit optimal function at much greater temperatures. Most of the low-temperature homologues of the hyperthermostable proteins would be [[Denaturation (biochemistry)|denatured]] above 60&nbsp;°C. Such hyperthermostable proteins are often commercially important, as chemical reactions proceed faster at high temperatures.<ref>[http://www.biomedcentral.com/1471-2164/7/186 "Analysis of Nanoarchaeum equitans genome and proteome composition: indications for hyperthermophilic and parasitic adaptation."]</ref>

 

The [[cell membrane]] contains high levels of [[saturated fatty acid]]s to retain its shape at high temperatures.{{citation needed|date=January 2010}}

 

 

* [[Strain 121]], an [[archaeon]] living at 121&nbsp;°C in the Pacific Ocean.

* ''[[Pyrolobus fumarii]]'', an [[archaeon]] living at 113&nbsp;°C in Atlantic hydrothermal vents.

* ''[[Methanopyrus]] kandleri'' strain 116, an [[archaeon]] in 80–122&nbsp;°C in a [[Central Indian Ridge]].

 

* ''[[Geothermobacterium ferrireducens]]'', which thrives in 65–100&nbsp;°C in [[Obsidian Pool]], Yellowstone National Park.

* ''[[Aquifex aeolicus]]''

* ''[[Thermotoga]]'', especially ''[[Thermotoga maritima]]''

==Notas==

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