As a scientist, I often find myself chatting with friends and neighbors about the latest advances in neuroscience. In the past few years I have found more and more people asking about microbiota—the microorganisms that typically inhabit a bodily organ. In the last 10 years, I’ve been one of many neuroscientists advancing new ideas about how microbiota in the gut affects brain function. The media has taken notice as well. Recent stories on the gut-brain axis—among the most exciting new frontiers in neuroscience—include “Some of My Best Friends Are Germs” in the New York Times Magazine and “Gut Microbes Contribute to Mysterious Malnutrition” in National Geographic. In 2012, the editors of Science thought the research important enough to devote a special issue to the topic.
Why is the issue so fascinating? For one thing, it’s heightened consciousness of how diet and nutrition impact our health. For another, it’s sheer numbers. Our brains contain billions of neurons, but we less often talk about the fact that trillions of “good” bacteria are alive and well in our intestinal tracts. Remarkably, these naturally occurring, ever-present commensal bacteria may be instrumental in how our brain develops, how we behave, react to stress, and respond to treatment for depression and anxiety.