Thermostable DNA polymerases

Dr Mullis understood that a decisive limit to the success of the amplification reaction was the destruction by heating of the DNA polymerase enzyme that had to continually be added during each cycle of the process since it did not endure the high temperatures of the PCR cycles. In fact, when he started experimenting in the Eighties he used a DNA polymerase extracted from the micro-organism E. coli, that was thermolabile and got destroyed at 94°C.
Hence another revolution took place when a few years later a thermophilic micro-organism, Thermus aquaticus was discovered. The latter was capable of living even in boiling water springs. The thermoresistant polymerase of these bacteria, called Taq polymerase, remained active even at 94° C: therefore it could be added just once, at the beginning of the reaction.
Nowadays, in all laboratories in which PCR analyses are carried out on DNA samples, thermostable DNA polymerase enzymes are used.
Nowadays the DNA polymerase, isolated from the thermophile bacterium Thermus aquaticus,  discovered in the thermal springs of Yellowstone Park, is produced with a technique of recombining DNA  in E. coli. In practise, bacteria of E. coli are used as producers of the enzyme Taq polymerase thanks to genetic manipulation that induces E. coli to produce an enzyme identical to the one that Thermus aquaticus produces in the extreme conditions in which it lives.

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