Question

The polymerase chain reaction was originally designed/run using the polymerase from E. coli. What type of organisms gave rise to the 'new' class of polymerases that streamlined the PCR procedure? Psychrophiles Thermophiles Alkalophiles Acidophiles

Answer 1

Thermophiles

Thermophiles are organisms that survive and grow at high temperatures ranging between 41^oC and 122^oC. These bacteria are tolerant to temperature and are evolved such that they can perform their metabolic processes normally at elevated temperatures.

The polymerase chain reaction is used for the purpose of amplification of DNA. IN PCR, a small amount of DNA can be amplified and billion copies of that DNA can be obtained. The procedure involved the steps of denaturation of the DNA strand, annealing of the PCR primers to the DNA strands and extension of the primer. For the extention of the primer, a DNA polymerase is required which extends the primer to produce the new DNA strand. The extension step is carried out at a tempertaure of 72^oC. At this temperature, most of the proteins get denatured and loose their activity. The polymerase from E.coli was used for extension step primarily but there was a need for a polymerase which remains stable and active at tempertaure of 72^oC.

Therefore, the DNA polymerase was derived from the thermophilic bacteria Thermus aquaticus and was called as Taq polymerase. Taq polymerase is active at 72^oC and has been employed extensively for PCR procedures.