To use all functions of this page, please activate cookies in your browser.
With an accout for my.bionity.com you can always see everything at a glance – and you can configure your own website and individual newsletter.
- My watch list
- My saved searches
- My saved topics
- My newsletter
Thermophilus aquaticus is a species of bacterium that can tolerate high temperatures; it is the source of the heat-resistant enzyme Taq DNA Polymerase, one of the most important enzymes in molecular biology because of its use in the polymerase chain reaction. Thermophilus aquaticus is one of several thermophilic bacteria that belong to the Deinococcus-Thermus group.
Additional recommended knowledge
When studies of biological forms in the Yellowstone hot springs began in the 1960s, scientists thought that the life of thermophilic bacteria could not be sustained in temperatures above about 55 degrees Celsius (131 degrees Fahrenheit). Soon, however, it was discovered that many bacteria in different springs not only survived but also thrived in higher temperatures. In 1969, Thomas Brock and Hudson Freeze of Indiana University reported a new species of thermophilic bacterium which they named Thermophilus aquaticus. The bacterium was first discovered in the Great Fountain region of Yellowstone National Park and has since been found in similar thermal habitats around the world.
It thrives at 70 degrees Celsius (160 degrees Fahrenheit), but can survive at temperatures of 50 to 80 °C (120 to 175 °F).This bacteria is a chemotroph, meaning that it performs chemosynthesis in order to obtain food. However, since its range of temperature overlaps somewhat with that of the photosynthetic cyanobacteria that share its ideal environment it is sometimes found living in conjuncture with its neighbors, obtaining energy for growth from their photosynthesis.
Enzymes from T. aquaticus
T. aquaticus was to eventually become famous as a source of thermostable enzymes, particularly the "Taq" DNA Polymerase, as described below.
Works of Kary Mullis
In the early 1980s Kary Mullis was working at Cetus on the synthesis of DNA. There was interest there in developing methods for detecting gene mutations that would be useful in disease screening. A major problem was that the available techniques (such as oligomer restriction) relied upon having a lot of DNA copies of the mutated gene. Mullis was familiar with the idea of using DNA oligonucleotides and hybridizing them to target DNA strands.
Idea Number One: PCR
In 1983, to advance a project he was involved with, Mullis began to consider using two oligonucleotides, one to hybridize to each strand of a DNA double helix. At first, his only reason for adding DNA polymerase to his experiments was as a way of making sure that deoxynucleoside triphosphates would be removed from his samples. But he then realized that the enzyme might make useful copies of the oligonucleotide-primed DNA strands. He immediately realized this was a potential way to amplify a region of DNA.
The main problem was, that after a round of strand copying, the DNA would have to be heated to near boiling in order to denature the newly formed double stranded DNA, allowing the strands to separate and open new templates for another round of amplification. This heating step would denature and inactivate the DNA polymerase, requiring that new enzyme be added at each amplification step.
This original PCR technique was slow and labor-intensive. The "inside-the-box" thinkers at Cetus began to automate the process. The first PCR machine, "Mr. Cycle" automatically added more enzyme after every heating and cooling step.
Idea Number Two: Thermostable Taq Polymerase
Those who know Mullis, such as Thomas J. White, agree that it was Mullis who came up with the idea of using Taq polymerase in order to avoid having to add polymerase to the PCR reaction during the thermocycling process. This was the key idea that made the PCR technique available to an army of molecular biologists.
Roche Molecular Systems eventually bought the PCR patents from Cetus for $300,000,000. Kary Mullis got $10,000 from Cetus and a Nobel Prize from his scientific peers. Research scientists and biotechnology companies spend hundreds of millions of dollars each year for Taq polymerase.
A 1988 article describing the use of Taq polymerase for PCR led to Science magazine naming Taq polymerase its first "Molecule of the Year" in 1989.
Figure: PCR Publications by Year.
The PCR technique became a major tool for molecular biology after the Taq DNA Polymerase and thermocyclers became available.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Thermus_aquaticus". A list of authors is available in Wikipedia.|