Microscopic worms that feasted on genetically engineered bacteria might shed light on why people gain weight. Biologists used this bacterial diet plan to turn off individual genes in the worms in order to identify ones that influence the animal's fat.
Investigators recently engineered around 17,000 strains of the bacterium Escherichia coli so that each strain makes an extra RNA strand that corresponds to a specific worm gene. When a worm consumes a particular E. coli strain, the additional RNA shuts down the corresponding worm gene through a phenomenon called RNA interference (SN: 10/19/02, p. 254: Bacterial diet quiets worm genes).
Gary Ruvkun of Massachusetts General Hospital in Boston and his colleagues used this library of bacterial strains to search for worm genes that could reflect human genes involved in obesity. With the help of a dye that marks fat droplets in living worms, the scientists monitored the fat storage of w