One of the most important molecular science inventions in the last century is the Polymerase Chain Reaction (PCR), also known as a thermocycler. This technique, which allows scientists to duplicate specific DNA sequences, owes its existence to two key figures and a natural phenomenon: microbiologist Thomas Brock, biochemist Kary Mullis, and the thermal Mushroom Pool at Yellowstone National Park.
The Discovery of Thermus aquaticus
The journey to PCR’s success began in the 1960s when microbiologist Thomas Brock discovered a heat-resistant bacterium in Yellowstone National Park. He found Thermus aquaticus strain YT-1 thriving in the Mushroom Pool, a hot spring with waters exceeding 70°C (158°F). This bacterium’s enzymes had evolved to survive and function in extreme heat. This makes it a thermophile, which is a property that would later prove essential to the success of PCR.
At the time, Brock's discovery was significant to his research, aimed at understanding life in extreme environments. It allowed the realization that life couldn’t be capped at certain temperatures. However, he probably didn’t expect his bacteria to once again make headlines decades later.
Taq-Polymerase
Fast forward to the late 1980s: Biochemist Kary Mullis was seeking a more efficient method to analyze DNA. The challenge he faced was replicating DNA strands in a laboratory setting, which required high temperatures to separate DNA strands and enzymes to synthesize new ones. The enzymes available at the time couldn’t withstand the heat, needing constant replenishment—a process usually reserved for interns.
Mullis turned to the archives of the American Type Culture Collection and decided to experiment with the thermophile Thermus aquaticus discovered by Brock years earlier. He cultivated batches of the bacterium and successfully extracted an enzyme, Taq polymerase. This enzyme proved perfect for PCR: it could withstand the high temperatures needed to separate DNA strands while also synthesizing new DNA copies.
With Taq polymerase, Mullis transformed PCR into a practical, fast process. PCR has three steps: denaturation, annealing, and elongation. Heat is required for each one and taq allowed the process to continue unhindered. This breakthrough earned him the Nobel Prize in Chemistry in 1993, as PCR became one of the most indispensable tools in science. Learn more about the PCR process here.
The Big Deal
Taq polymerase eliminated the need to replace enzymes after each heating cycle, significantly simplifying and accelerating DNA amplification.
This advance revolutionized PCR, enabling its application across many fields. It plays a central role in sequencing the human genome, understanding hereditary diseases, and advancing gene editing technologies like CRISPR. It can even amplify tiny DNA samples, making it invaluable for forensic teams investigating crime scenes.
Taq and PCR have allowed molecular science to advance dramatically. It serves as a reminder that the natural world has everything we need- if one knows where to look.
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