The optimal growth temperature for Thermus aquaticus is 70 °C. This bacterium is a thermophile, meaning it is adapted to grow at temperatures far hotter than those preferred by ordinary environmental bacteria.
Thermus aquaticus was first isolated from hot springs in Yellowstone National Park. The original studies found that it can grow across roughly 40–79 °C, with growth strongest at about 70 °C. It is an aerobic, non-spore-forming, rod-shaped bacterium and often produces a yellow or orange pigment.
The species became famous because it produces Taq DNA polymerase, an enzyme that remains stable during the high-temperature steps of polymerase chain reaction. PCR repeatedly heats DNA to around 94–98 °C to separate its strands, so ordinary DNA polymerases would be damaged. Taq polymerase made automated thermal cycling practical and helped revolutionize genetics, diagnosis, and forensic science.
The 70 °C figure refers to the bacterium’s growth optimum, not necessarily the best temperature for every reaction involving its enzymes. Taq polymerase itself is commonly used around 72 °C during DNA extension, a nearby but distinct measurement.