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Fall 2009
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Ruth Ley Earns Beckman Award for Study of Gut Bacteria

By Chris Bentley ’10

Professor Emeritus Ed Oyer, left, with
Professor Ronnie Coffman
Robert Barker

Ruth Ley

Microbiologists know that diversity is not only skin deep. In fact, CALS assistant professor Ruth Ley thinks that a person’s mix of microbes—which outnumber human cells ten to one in the body—could be as important to certain aspects of people’s health as are their genes.

Ley, who joined the Department of Microbiology in 2008 from Washington University in St. Louis School of Medicine, is one of 11 scholars nationwide to receive the 2009 Arnold and Mabel Beckman Foundation Young Investigator award. This award will support her work on how defensins, a particular kind of antimicrobial peptide produced in the intestine, influence the diversity of bacteria in the gut. Ley was also selected a 2009 Pew Biomedical Scholar, but declined in light of the Beckman Award.

In past studies, Ley and her colleagues have shown that the composition of microbial communities in the gut can impact host health. For instance, obesity is associated with a reduced diversity of gut microbiota. She and her colleagues observed that sterile mice fed with gut bacteria from fat mice gained more weight than the same mice fed with bacteria from lean mice—and who had otherwise the same diet.

“Mice that are completely germ-free are resistant to diet-induced obesity—you can’t overfeed them and make them fat . . . but the second you put a bug in there, their metabolism changes,” Ley explains.

While gut bacteria come from only three main groups—Firmicutes, Bacteroides, and Actinobacteria—the mix of species present can differ dramatically from one person to the next. Evidence suggests that a shared early environment may lead to intermingling microbes, though Ley says, “Even family members are still pretty different.”

“If we just grab the functional genes out of that mix, we’re going to end up with the same functions, but they’re carried on a whole bunch of different strains for different people,” she says. “Think of cars—they’ve all got a chassis and wheels, but there are all these different makes . . . though they all have the same functions, more or less.” The microbiome of obese mice and humans, for example, may have a heightened capacity for storing energy, so that the host holds more energy—and gains more weight—than would a lean individual eating the same diet.