Focus on Aging

Kenyon found Horvitz's roundworms fascinating because their development could be traced cell by cell, and she decided that she would

This tiny roundworm, Caenorhabditis elegans, lives in soil and eats bacteria. Scientists have studied its genes extensively, uncovering important information about development and aging. (Maria E. Gallegos)

Other Scientists: Sydney Brenner (1927- )

Sydney Brenner was born in 1927 near Johannesburg, South Africa, to Jewish parents who had emigrated from eastern Europe. He worked with Francis Crick at Cambridge University in the late 1950s and early 1960s to discover how cells use the "genetic code" in DNA molecules to construct proteins. Brenner then turned to researching the way genes influenced animals' development before birth, using C. elegans as his test subject.

During the next two decades, Brenner, his coworkers, and other laboratories inspired by him worked out the worm's development, cell by cell. By studying mutations, they determined which genes guided cells to certain places in the worm's body, which genes told cells to mature into different types such as nerve or muscle, and which genes told cells to die. The researchers located these genes on the nematode's chromosomes and worked out the sequence of bases in some of them, a process that at the time was extremely tedious and time-consuming. According to Andrew Brown's history of C. elegans research, the body of knowledge about this tiny worm that Brenner and his followers accumulated was the inspiration for similarly detailed studies of other multicelled creatures and eventually led to the Human Genome Project. In 1998, C. elegans became the first multicelled organism to have its complete genome sequenced.

Sydney Brenner won a share of the Nobel Prize in physiology or medicine in 2002 for his work on the way genes orchestrate an organism's development. He shared the prize with John Sulston and Bob Horvitz, the scientist who introduced Cynthia Kenyon to C. elegans.

rather study them than bacteria. After she finished her Ph.D. work in 1981, her interest in the worms took her to Cambridge to work under Sydney Brenner. She spent five years there studying how the nematodes developed before birth, and then returned to the United States and joined the University of California, San Francisco (UCSF), in 1986 as an assistant professor. She became a full professor of biochemistry and biophysics in 1992.

The focus of Kenyon's studies changed around 1990, when she happened to pick up a petri dish that she had meant to discard a month earlier. The dish contained mutant worms that did not reproduce well, so it was not as crowded as such dishes normally would be. Most of the worms left in it were old, nearing the end of their 20-day lifespan. "I had never seen an old worm. I had never even thought about an old

Parallels: The Discovery of Penicillin

Cynthia Kenyon was not the first scientist whose career was changed by a forgotten laboratory dish. In 1928, the Scottish bacteriologist Alexander Fleming, showing a friend around his London laboratory, passed a stack of petri dishes that had gone uncleaned while Fleming was on a recent vacation. According to Gwyn Macfarlane's biography Alexander Fleming: The Man and the Myth, Fleming picked up one dish, looked at it hard, and said to his friend, "That's funny." The dishes contained colonies of staphylococci, a type of bacteria that infects wounds. Fleming noticed that a speck of mold, or fungus, similar to the blue mold that sometimes grows on stale bread, had landed on this dish—and around the mold was a clear area, showing that no bacteria grew there.

Fleming went on to study the mold that had "spoiled" his culture dish and the bacteria-killing substance that the fungus produced. The mold belonged to a group called Penicillium, so he called the "mold juice" penicillin. Fleming published a paper on the mold and its chemical in 1929, but he did not pursue his research for long after that. He concluded that penicillin would be worthless in medicine because he could not purify it, and in impure form it lost its effectiveness quickly. Ten years later, however, two Oxford University scientists, the Australian-born pathologist Howard Florey and Ernst Chain, a biochemist who had recently fled Nazi Germany, read Fleming's paper and decided to reinvestigate penicillin. Using improved techniques, Chain purified the germ-killing part of the "mold juice," and Florey's research group showed that the purified substance could stop the growth of dangerous bacteria in the bodies of mice and humans. American drug companies built on the Oxford team's work to mass-produce penicillin in the early 1940s. As the first antibiotic to be widely used, penicillin saved millions of lives in World War II and revolutionized the treatment of infectious diseases.

worm," Kenyon later told U.S. News & World Report writer Nell Boyce. Nonetheless, the young scientist had no trouble recognizing these nematode senior citizens: They were shrunken and wrinkled, and they moved much less vigorously than young worms. "I felt sorry for them," Kenyon said to Boyce. They reminded her that she was growing older, too, she told the reporter. "And right on the heels of that [thought], I thought, 'Oh, my gosh, you could study this.'"

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