While traditionally considered notorious, what if some bacteria actually help the immune system rather than harm it? Caltech microbiologist Sarkis Mazmanian describes his efforts to harness the good bugs in our guts to improve health for people with Parkinson's, Alzheimer's, and autism—his idea once dismissed as a "hunch" but now gaining acceptance from scientists and society.

Sarkis Mazmanian is the Luis B. and Nelly Soux Professor of Microbiology and a Heritage Medical Research Institute Investigator at Caltech.