Nitric oxide, the versatile gas that helps increase blood fl ow, transmit nerve signals, andregulate immune function, appears to perform one more biological feat — prolonging the life ofan organism and fortifying it against environmental stress, according to a new study. The study reveals that a roundworm called Caenorhabditis elegans, an animal widely used in laboratory studies ofaging, lives signifi cantly longer when fed bacteria capable of manufacturing nitric oxide. The tantalizingobservation points to one of the mechanisms by which the microbiome, the trillions of microbial cells inhabitingour bodies, may play a vital role in our health.