Yellowstone National Park – birthplace of Taq

I’ve never been to Yellowstone National Park, but it’s on my list of places I want to visit, not only for the beautiful scenery and spectacular hot springs and geysers, but also because it’s the site of origin of one of the most famous molecules in molecular biology.

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Thomas Brock is a retired biologist who started his career in the early 1950s, as a microbiologist. He preferred the outdoors over the lab, so he started looking for opportunities to do more ecological studies, and in 1963 he launched a program focused on the study of  microbes living in geysers and hot springs. These pools were considered to be naturally occurring steady-state ecosystems. Sort of like a controlled lab setting, but outdoors. Brock hoped that organisms the hot water pools would allow him to better understand the physiological limits of photosynthesis, but he soon made a much more interesting discovery.

Brock took samples from springs at different temperatures, and found many more microbes than he originally thought possible. Some of them even lived at temperatures higher than 73°C, which was at the time thought to be the upper limit for life. One of the sites he studied was a spring in the Lower Geyser Basin, called Mushroom Spring. In October 1966, Brock isolated culture YT-1 of a new micro organism, from a sample he had collected in Mushroom Spring at a temperature of 73°C on September 5th. He initially called his new discovery Caldobacter trichogenes, but by the time the first article about the discovery was published, the name had already changed to Thermus aquaticus.

Together with other extremophiles that Brock found in Yellowstone, culture YT-1 was dutifully recorded, and sent to the American Type Culture Collection (ATCC) where it was made available for other scientists to study.

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In 1983, Kary Mullis, a scientist working at Cetus Corporation in California, had an idea to optimise the process of replicating small DNA samples in vitro. He developed a technique called PCR, or polymerase chain reaction, which uses temperature changes to unravel double stranded DNA, and small primer DNA sequences together with an enzyme called DNA polymerase to generate new strands of DNA on each half of the unraveled strand. Unravel those newly formed DNA strands, and the process starts over, each round doubling the amount of DNA.

One problem with this new technique was the the high temperatures required to unravel DNA also damaged the DNA polymerase. Other Cetus researchers set out to find a polymerase that could survive at the high temperatures needed for PCR.

All organisms have their own DNA polymerase, but our human version, for example, is optimized for our body temperature of about 37°C, and doesn’t survive extremely high temperatures. But organisms that live at high temperatures must also have polymerases that can stand the heat, and this is what they were looking for.

The researchers from Cetus analysed several of the samples that Brock had collected and deposited with ATCC, until they found what they were after in sample YT-1 of Thermus aquaticus – or Taq for short.

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The technology to rapidly replicate DNA samples using PCR with Taq polymerase revolutionised modern molecular biology and is an indispensable tool in forensics. Any research involving genetics, cloning, or identifying the function of new genes will at some point have involved the use of Taq polymerase. You’ve seen the technique in action in the fictional crime labs of Law and Order, CSI, and several other shows and movies. An advertisement for a PCR machine went viral online a few years ago. Taq polymerase was the molecule of the year in 1989, and Kary Mullis won the Nobel Prize in 1993 – but PCR would not have been possible without the bacteria that Thomas Brock isolated decades earlier from a hot spring in Yellowstone.

Taq polymerase was such a success, both scientifically and commercially, that National Parks changed its regulation about research on park grounds. They haven’t seen any money from the molecule that Mullis brought to fame, and are now working with agreements that state that benefits of any “bio-prospecting” on park grounds should be shared with National Parks.

And Brock? He didn’t get any money out of his discovery either, but he didn’t mind. As quoted in TIME magazine:

“Yellowstone didn’t get any money from it. I didn’t get any money, either, and I’m not complaining. The Taq culture was provided for public research use, and it has given great benefit to mankind.”

Brock was just in it for the science, and for the travel.