Taq polymerase, often abbreviated as Taq, is a deoxyribonucleic acid (DNA) polymerase that synthesizes new DNA strands. This enzyme facilitates DNA replication by adding nucleotides to a growing DNA chain. It extends a DNA strand by reading a template strand and incorporating complementary building blocks.
The Organism’s Natural Habitat
Taq polymerase is derived from Thermus aquaticus, a species of bacteria first identified in 1969. This bacterium is an extremophile, meaning it thrives in environments that are considered extreme for most life forms. Its natural habitat includes geothermal locations such as the hot springs of Yellowstone National Park, as well as hydrothermal vents around the world.
Thermus aquaticus flourishes in very high temperatures, typically between 70 to 80 degrees Celsius (158 to 176 degrees Fahrenheit), though it can survive at temperatures up to 95 degrees Celsius. This remarkable tolerance to heat is far beyond what most proteins and enzymes can withstand without losing their structure and function. The ability of Thermus aquaticus to thrive in such conditions is a result of specific biological adaptations that allow its cellular machinery, including its enzymes, to remain stable and active at elevated temperatures.
Discovery of the Enzyme
The journey to discovering Taq polymerase began with the pioneering work of American microbiologist Thomas D. Brock. In the 1960s, Brock embarked on studies of thermophilic microorganisms in the hot springs of Yellowstone National Park. His research revealed that microbial life could thrive in temperatures previously thought uninhabitable, even nearing boiling point. In 1969, Brock and his colleague Hudson Freeze reported the discovery of Thermus aquaticus.
Following the identification of the bacterium, the enzyme was isolated and characterized. In 1976, Alice Chien and her colleagues successfully purified a stable DNA polymerase from Thermus aquaticus. This enzyme, later named Taq polymerase, was found to have an optimal temperature for activity around 80 degrees Celsius.
The Enzyme’s Distinctive Characteristic
The most notable characteristic of Taq polymerase is its thermostability, which means it can maintain its structure and activity at high temperatures that would typically denature most other enzymes. Taq polymerase functions optimally at temperatures between 75 and 80 degrees Celsius and retains activity even after exposure to temperatures as high as 95 degrees Celsius.
This heat-stable property is important for its use in the Polymerase Chain Reaction (PCR), a technique that involves repeated cycles of heating and cooling. During PCR, DNA strands are separated at high temperatures (around 95°C), a process that would inactivate conventional DNA polymerases. Because Taq polymerase remains functional through these high-temperature denaturation steps, there is no need to add fresh enzyme in each cycle, simplifying and automating the PCR process. Its ability to withstand heat allows for efficient and consistent DNA synthesis throughout the multiple cycles required for DNA amplification.