Moderation and Mutation: The Legacy of Bruce Ames
Remembering Bruce Ames, renowned for creating the Ames carcinogenicity test, who passed away two years ago this week
Bruce Ames embodied the world’s perception of a scientist more than most. Smart, quirky, endlessly curious, he pushed ahead even when society deemed him suitable for retirement or “emeritus status.” Among the many ideas he successfully pursued, the one he will probably be best remembered for is the development of the “Ames Test“ for carcinogenicity in the 1970s.
The brilliance of the Ames Test lies in its simplicity. It tests whether exposure to a compound results in significant DNA-related mutational effects. The process begins with a mutant Salmonella bacterial strain that can’t produce the amino acid Histidine (HIS) but requires HIS to live. This strain is placed, along with a suspected carcinogen, on an agar plate with a small amount of HIS. This allows the bacteria a brief window to grow, giving the suspected carcinogen time to affect the living bacteria. If the carcinogen encourages mutation, some bacteria will mutate to produce HIS, and will thrive. If not, most bacteria will die off. The test is cheap, fast, and relatively accurate (initially flagging about 90% of known carcinogens, though as more carcinogens have been identified, that value has dropped).
The Ames test replaced costly and slow animal testing, which also raised ethical questions. It quickly led to the regulation of various carcinogens — the flame retardant Tris in children’s clothing, aflatoxins that develop in improperly stored grains and nuts, and dozens more in the decades since. Nearly half a century after it was developed, the Ames Test remains critically important as an initial screen in toxicology and environmental science.
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He never patented it — and sent the mutant strain to anyone who asked, choosing impact over income.
So how did the man who invented the test for carcinogens handle them in his own life? With a shrug.
I met Bruce Ames at a party on the Berkeley campus in the early 1980s, where I was a graduate student in chemistry and Ames was a professor of biochemistry. It’s funny how those whose names are now shorthand for an entire field were once just part of the day-to-day. At the time, there was mainstream concern over nitrites in bacon. As a bacon lover myself, I found this disconcerting — though not enough to stop eating bacon. I asked Bruce what he thought. His response has stayed with me all these years: “You can’t live your life worrying about carcinogens in modest amounts. Most things you eat or use have something that tests carcinogenic in it. Moderation works well. Oh, and I still eat bacon, too.”
About a decade later, Ames gave an interview to the LA Times in which he said basically the same thing, writ larger: “With all the scare stories, people don’t know what’s important anymore. And it turns out what’s important is what your mother told you: Don’t smoke, eat a good diet, settle down and live a moderate life. Your mother was right.”
He understood the difference between educated risk and absolutism. He lived that way all the way to 95. The man with the most reason to fear what’s on our plates never did.
He never gave up bacon.
