Human microbiome news! Researchers at McMaster University in Ontario, Canada, report evidence that bacteria residing in the gut influence brain chemistry and behavior . The researchers showed that disrupting the normal bacterial content of the gut with antibiotics produced changes in behavior in healthy adult mice. The animals became less cautious or anxious and showed an increase in brain derived neurotrophic factor (BDNF), which has been linked to depression and anxiety. When oral antibiotics were discontinued, the bacteria in the gut returned to normal, as did the animals’ behavior and brain chemistry. Check out the original article in the journal Gastroenterology .