Dr. Christopher Johnston is a microbiologist who focuses on human microbiota, the trillions of bacteria that live on us and within us, and he is particularly interested in those that inhabit the mouth and the gut. While most of these species are harmless or even beneficial, some are implicated in oral and lung infections, cardiovascular disease, and cancer. He designs new genetic engineering approaches that allow his lab and researchers around the world to uncover how bacteria behave during infection, how they acquire resistance to antibiotics and how they can be engineered to produce molecules for human use.