January 28th, 2015
We’ve talked a lot about genomic sequencing and its potential for ushering an era of truly personalized medicine. But sequencing requires an ample supply of DNA. And that supply comes from a simple chemical reaction that forms the basis of nearly every modern genetics experiment. What isn’t so well known is that its discovery owes a lot to a microbiologist who loved to travel, some refuted assumptions of what can live in hot springs, and a now-closed field station in Yellowstone National Park.
The reaction, called the polymerase chain reaction (PCR) was created in the 1980s (and Kary Mullis won the Nobel Prize in Chemistry for inventing it). But much earlier, in the 1960s, Thomas Brock was a biologist at Indiana University whose interest was shifting toward microbial ecology; he began studying microorganisms in intertidal pools, freshwater lakes, cold springs, and finally, geysers and hot springs.
Brock had a travel bug, and was increasingly interested in doing field ecology. He started a field research station in Yellowstone National Park, though he says at first he wasn’t interested in geysers. At the time, scientists believed that bacteria optimally lived at about 55°C, and that nothing lived above 73°C. So, he assumed there was nothing to find.
But, he soon found pink bacterial filaments living in the Octopus Hot Spring at temperatures above 80°C. The bacteria: Thermus aquaticus, which contains the DNA polymerase (the enzyme that builds DNA) that ultimately became the backbone of PCR.
The key to making PCR work is a heat-tolerant enzyme that can endure conditions in the chain reaction. Since Thermus aquaticus was the first organism known to exist (and reproduce) at these high temperatures, it naturally became the focus point of Mullis’ later invention.
In a Journal of Bacteriology paper with an honors undergraduate Hudson Freeze (now at the Burnham Institute in La Jolla, Calif.), Brock introduced the new species in 1969. It was the first instance of an organism thriving at extremely high temperatures.
T. aquaticus, it turned out, is ubiquitous at high temperatures. Brock found the bacteria in hot springs in California, soil in a tropical-temperature greenhouse, and even the hot water supply at Indiana University!
The bacteria are also in hot springs worldwide, including Japan, New Zealand, and Iceland. But Yellowstone was the easiest to study; being a national park, habitats were not destroyed or developed into spas and resorts, which made international research challenging. Ironically, Brock at first had no interest in Yellowstone, because of the park’s reputation in the 1950s and 60s as more of an amusement park than natural habitat.
Brock continued his work on extreme thermophiles, but closed the Yellowstone research station in 1975. Only several years later, when PCR technology—which depends on the heat-tolerant DNA polymerase found in Taq—was announced did interest in his work rebound.
Sources: Thomas Brock, Life at High Temperatures
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