The Missing Link

Completing the Triton story of Taq and PCR

In 1968, Hudson Freeze, MS ’71, PhD ’76, (right, middle) co-discovered Thermus aquaticus with Thomas Brock in a hot spring at Yellowstone National Park. The microbe would optimize the polymerase chain reaction (PCR) and revolutionize DNA science. See

Three people kneeling on the ground with a small stream in front of them and another person on the opposite side. They're in a dry area with a few lanky trees populating their background.
In 1968, Hudson Freeze, MS ’71, PhD ’76, (pictured at right, middle) co-discovered Thermus aquaticus with Thomas Brock in a hot spring at Yellowstone National Park. The microbe went on to optimize the polymerase chain reaction (PCR) and revolutionize DNA science. 

Can you tell us how you came to discover Thermus aquaticus (Taq)?

I was an honors student in microbiology at Indiana University when my mentor suggested that I talk to Dr. Thomas Brock about working in his lab. Almost immediately, I was invited on his research trip to Yellowstone. That was a big deal for me, as I’d never even been out of Indiana!

Once out there, I started working in the lab—just a little house with some equipment, really. We went to the springs every day to take samples for about a month. Back at the university, I began putting samples from various springs into test tubes with different kinds of media and incubated them at a high temperature. Nothing happened for three or four days until I picked one up and swirled it and little crystals came up off the bottom.

I thought little of it until a couple of days later when the crystals looked slightly different. I put some under a slide and suddenly saw all these worms of bacteria crawling around. Even now, I get goosebumps thinking about seeing that under the microscope. I realized I was the first person in the world to see the organism we eventually named Thermus aquaticus. Out of that came a couple of papers, which ended up getting me into UCSD for graduate school, where my roommate was headed.

What do you recall from your UC San Diego days?

I was there as a graduate student for six years, working with Bill Loomis, who had started as a faculty member about three or four years before I arrived. When I finished my PhD in biology, I actually went to L.A. to try out acting. I did some commercials, but I really missed science and I realized how fulfilling it was. So I came back and did a postdoc in the department of medicine and then a few in neuroscience until 1988, when I came to where I am now at Sanford Burnham Prebys, then called the La Jolla Cancer Research Foundation.

What do you do there?

A lot of what I did as a graduate student put me in an area called glycobiology—the study of the biology and chemistry of sugar chains that are added to proteins. Over time, I happened to meet folks with kids who were affected by rare disorders that result from genetic mutations in one of the hundreds of steps needed to make sugar chains. So even without being medically trained, I found I could actually help these families. In fact, I make great use of PCR to get down to the specifics of where there are mutations, what the genes are, and determining what therapies might help. We then bring the results from these cases back to the lab to understand the basis of that therapy and why it works or not, in order to better inform our overall concepts. In all, I’d say our lab has probably helped at least 350 or more patients.

Taq has since forever impacted DNA science—how does that feel?

I mean, who ever thought anything like that could happen? I’ve always viewed myself as a basic science guy—someone who’s just curious. That curiosity and fascination is oftentimes why people do science, and many times, just that is enough. But it’s amazing when you think of all that has been changed by PCR, and CRISPR too. My feeling is that if you discover something, you discovered it because the rest of the scientific enterprise enabled you to do so. And it’s extremely fulfilling to have given something back to that enterprise so that others can utilize it and end up giving back to the whole world in a very profound way.

 What do you love about science and the work you do now?

I’m still infatuated with the idea that you never know what’s going to be around the corner. There’s organization and planning and foresight in experiments, of course, but I really live for those serendipitous events that can really be life-changing, whether in discovery science or just meeting people who you may be able to help. It’s amazing as well to learn from those people in the course of your work. They end up giving back to the process as well. It’s just this big circle—we all do this together.

 Speaking of circles, have you been back to Yellowstone?

In 2007, I went back to the park for the first time since I went with Tom Brock. I visited the spring and brought the same picture of it that was taken in 1966. And even then, over 40 years later, it was the same spring—nothing had changed, really. I walked about 50 yards away and was sitting down when a couple walked by looking at a map and they asked, “Excuse me, we think that somewhere around here is the hot spring where that one bacteria was discovered. Do you have any idea where that might be?” I said, “Oh, yeah—I’m pretty sure it’s right over there.”