A Yellowstone hot-spring microbe made modern DNA testing possible

In the 1960s, biologist Thomas Brock was studying the scalding pools of Yellowstone National Park, where many springs approach boiling. Conventional wisdom held that nothing could live above about 55 degrees C. Brock and undergraduate Hudson Freeze proved otherwise, isolating a bacterium that thrived between 65 and 70 degrees C (149 to 160 F). They named it Thermus aquaticus.

The microbe’s superpower was a heat-stable enzyme, Taq polymerase, that keeps copying DNA at temperatures that wreck ordinary proteins. That mattered because the technique it enabled, the polymerase chain reaction (PCR), works by cycling samples through three temperatures: about 95°C to split the double helix apart, roughly 55°C to let short primers bind, and around 72°C for the enzyme to extend new strands. Each cycle doubles the DNA, so a handful of molecules becomes billions in a couple of hours.

The catch is that 95°C step. Earlier polymerases were destroyed by it, forcing researchers to add fresh enzyme by hand every single cycle — Taq simply shrugs it off.

Using Taq, biochemist Kary Mullis at the Cetus Corporation developed PCR, earning the 1993 Nobel Prize in Chemistry.

The payoff was enormous, and so were the fights over it. Cetus sold the PCR patent rights to the drug company Roche for $300 million in 1991, kicking off years of bitter litigation over who owned the method. Later thermophiles yielded even better enzymes — Pfu polymerase, for instance, copies DNA with higher fidelity. But it all traces back to a bacterium in a hot spring that most people would never have noticed.