The steaming, colorful pools and explosive geysers of Yellowstone National Park give it an otherworldly beauty. But the colors in Yellowstone’s hot-water springs are not just pleasing to look at and photograph; amazingly, they are also why we have accurate tests for diseases in addition to new drug therapies and vaccines.

Just over 60 years ago, Thomas Brock was on a cross-country road trip when he stopped for a break in Yellowstone. Standing at the edge of Mushroom Pool, in the Lower Geyser Basin of Yellowstone National Park, the microbiologist noticed that there were microorganisms, such as algae, growing in the hot spring — which was surprising given how hot the water is in Yellowstone’s pools and geysers. The temperature of Mushroom Pool is over 150 degrees Fahrenheit; when we soak ourselves in a hot tub, the water temperature is usually between 100 and 104 degrees Fahrenheit.

Brock wanted to know how these heat-loving microbes (known as “thermophiles”) prospered in Yellowstone’s extreme environment. Over the next few years, with support from the National Science Foundation, he and his student Hudson Freeze took and studied samples from the pools in the park.

They named one of the yellow thermophiles living from the park “Thermus aquaticus,” and discovered that its enzymes — molecules that speed up chemical reactions — have an unusual property, which is that they do not fall apart at high temperatures. One of the Thermus aquaticus enzymes that is not bothered by the hot temperatures, Taq polymerase, has the job of replicating the microbe’s DNA.

This heat-resistant enzyme is now at the heart of methods used in medical and research laboratories around the world, when trying to make a lot of DNA in a very short amount of time. The technique is called the polymerase chain reaction, or PCR for short. PCR relies on cycles of heating and cooling to copy strands of DNA millions or billions of times, and requires enzymes that can withstand the heat.So why do we need billions of copies? Turning small samples of DNA into large ones makes it possible for doctors and scientists to identify diseases and to test new drug therapies and vaccines.

PCR is a core biological technology, not only used in medicine. It is also used in agriculture to identify genetically modified organisms in food and to detect pathogens, in environmental science to track biodiversity and monitor pollutants, and in forensic science to allow for identification from trace amounts of DNA. Its impact was recognized by a Nobel Prize in Chemistry in 1993. Thermus aquaticus should be proud.