Thermus aquaticus

Thermus aquaticus is a species of bacteria that can tolerate high temperatures, one of several thermophilic bacteria that belong to the Deinococcus–Thermus group. 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 (PCR) DNA amplification technique. When studies of biological organisms in hot springs began in the 1960s, scientists thought that the life of thermophilic bacteria could not be sustained in temperatures above about 55 °C (131 °F). Soon, however, it was discovered that many bacteria in different springs not only survived, but also thrived in higher temperatures. In 1969, Thomas D. Brock and Hudson Freeze of Indiana University reported a new species of thermophilic bacteria which they named Thermus aquaticus. The bacterium was first isolated from Mushroom Spring in the Lower Geyser Basin of Yellowstone National Park, which is near the major Great Fountain Geyser and White Dome Geyser, and has since been found in similar thermal habitats around the world. It thrives at 70 °C (158 °F), but can survive at temperatures of 50 °C to 80 °C (122 °F to 176 °F). This bacterium is a chemotroph—it performs chemosynthesis 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 jointly with its neighbors, obtaining energy for growth from their photosynthesis. Thermus aquaticus is generally of cylindrical shape with a diameter of 0.5 μm to 0.8 μm. The shorter rod shape has a length of 5 μm to 10 μm. The longer filament shape has a length that varies greatly and in some cases exceeds 200 μm. The rod-shaped bacteria have a tendency to aggregate.Associations of several individuals can lead to the formation of spherical bodies 10 μm to 20 μm in diameter, also called rotund bodies. T. aquaticus has become famous as a source of thermostable enzymes, particularly the Taq DNA polymerase, as described below. Studies of this extreme thermophilic bacterium that could be grown in cell culture was initially centered on attempts to understand how protein enzymes (which normally inactivate at high temperature) can function at high temperature in thermophiles. In 1970, Freeze and Brock published an article describing a thermostable aldolase enzyme from T. aquaticus. The first polymerase enzyme isolated from T. aquaticus in 1974 was a DNA-dependent RNA polymerase, used in the process of transcription. Most molecular biologists probably became aware of T. aquaticus in the late 1970s or early 1980s because of the isolation of useful restriction endonucleases from this organism. Use of the term Taq to refer to Thermus aquaticus arose at this time from the convention of giving restriction enzymes short names, such as Sal and Hin, derived from the genus and species of the source organisms.