Thermits aquaticus

Fig. 4.1.2. A. Structure of Thermits aquaticus (Taq) DNA polymerase bound to the DNA primer-template complex. B. "Open and closed conformation after dNTP binding of Taq DNA polymerase. Structures were built on PDB entries 3KTQ and 4KTQ. 

The PCR is a three-step cyclic process that repeatedly duplicates a specific DNA sequence, contained between two oligonucleotide sequences called primers (154,155). The two primers form the ends of the sequence of DNA to be amplified and are normally referred to as the forward and reverse primers. The forward primer is complementary to the sense strand of the DNA template and is extended 5 to 3 along the DNA by DNA polymerase enzyme (Fig. 27). The reverse primer is complementary to the antisense strand of the DNA template and is normally situated 200-500 base pairs downstream from the forward primer, although much longer sequences (up to 50 kbase) can now be amplified by PCR. The process employs a thermostable DNA polymerase enzyme (such as the Taq polymerase from Thermits aquaticus BM) extracted from bacteria found in hot water sources, such as thermal pools or deep-water vents. These enz5unes are not destroyed by repeated incubation at 94 °C, the temperature at which all double stranded DNA denatures or melts to its two separate strands (155). 

Although Thermits aquaticus grows under conditions that would be impossible for most other life forms, its environment seems tame in comparison with that recently described for a series of methanogenic bacteria... 

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