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Extremophiles are organisms that thrive in (and may require) extreme environments. Most known extremophiles are microbes. Those that thrive in very hot environments are called thermophiles or hyperthermophiles, while those that thrive in very salty environments are called halophiles. Extremophiles can be contrasted with organisms that live in less extreme environments. Such organisms may be called mesophiles (living at moderate temperatures) or neutrophiles (living at neutral pH).

Proteins of thermophiles and halophiles tend to be more stable, easier to manage in the laboratory, and easier to crystallize than proteins from mesophiles. Salt bridges are more numerous in these proteins, contributing to their stabiliity. Consequently, extremophile proteins have been very useful in crystallography and structural genomics, yielding many new structures[1][2]. For example, the Nobel Prize-winning structures of the ribosome were determined using proteins from the thermophile Thermus thermophilus and the halophile Haloarcula marismortui (see 2009 at Nobel Prizes for 3D Molecular Structure#Twenty-First_Century).

Most applications of the polymerase chain reaction (PCR) method now rely on thermostable Taq Polymerase, an enzyme from Thermus aquauatics - see 1taq, 1tau, 1bgx; Kary Mullis shared the 1993 Nobel Prize in Chemistry for the invention of PCR.

Even before the use of the extremophile's enzymes as tools and models in the lab, the biological analysis of these diverse organisms had a profound effect on how scientists thought about evolution of life on our planet and phylogenetic relationships, perhaps best illustrated by Carl Woese's work to classify life into three Domains: Archaea, Bacteria, and Eukaryota.

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External Resources


  1. Jenney FE Jr, Adams MW. The impact of extremophiles on structural genomics (and vice versa). Extremophiles. 2008 Jan;12(1):39-50. Epub 2007 Jun 13. PMID:17563834 doi:10.1007/s00792-007-0087-9
  2. Cava F, Hidalgo A, Berenguer J. Thermus thermophilus as biological model. Extremophiles. 2009 Mar;13(2):213-31. Epub 2009 Jan 21. PMID:19156357 doi:10.1007/s00792-009-0226-6

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