why do researchers use dna polymerase from a bacterium found in superheated water for pcr?

Question

I have found out what the bacterium is called, but no article I have read states as to why researchers use it- just states that they use it. It wasn't much of a help. :(

Answer 1

Because during PCR, the solution is heated repeatedly above the point where most proteins denature (unfold and become ineffective). We use polymerase from a thermophilic bacterium because it has evolved to withstand the higher temperatures and can continue to function through repeated heating/cooling cycles as in PCR.

Answer 2

Taq is thermostable, it can withstand high temperatures. Any organism that lives near a heat vent would need proteins to do this to survive. As PCR has the objective of amplifying a specific piece of DNA, and DNA polymerases work by copying single-stranded DNA making its complementary sequence the thermostability is absolutely needed. Why? Genomic DNA is pretty stable, need high temperatures to dissociate the strands from dsDNA to ssDNA. Also in order to copy any piece of DNA we need an existing piece of DNA (the primer) bound to the genomic ssDNA for Taq to add nucleotides on to. Wtih PCR we supply this, and since small pieces of DNA reanneal faster than larger pieces, the genomic ssDNA, the primers bind first to when we cool from 92C to 55/60C. As Taq does not work at these two temps, and only at 72C when the primers are bound to target DNA we should amplify only our target sequence. The only thing to worry about is mispriming.

Answer 3

To add to the above; the PCR cycle has 3 steps: 1) denature at 95C. This separates the two strands of the DNA. At this temp Taq is inactive 2) Primer binding at 55C. At this temp, primers bind to each strand, but presumedly Taq isn't very active, 3) Primer extension at 72C. Taq is optimally active, and able to produce the opposite strand.. Repeat 1-3 30 cycles.