Billie Iverson, 86, of Cranston, R.I., recently underwent a transplant of intestinal microbes that likely saved her life. Ryan T. Conaty for NPR hide caption

toggle caption Ryan T. Conaty for NPR

Microbiologist Emma Allen-Vercoe invented the Robogut, a mechanical device that mimics conditions in the human colon. Courtesy of hide caption

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Packages of Activa yogurt, which contain probiotics, on a grocery shelf in Chicago. M. Spencer Green/AP hide caption

toggle caption M. Spencer Green/AP

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