The microbial makeup of a newborn baby’s intestines has changed dramatically over the past 100 years, and we are now beginning to understand how and why this matters.

Our resident bacteria can affect the activity of immunotherapies and other medicines in the body.

Through their effects on metabolism and immunity, bacteria in the gut affect whether medications will be effective for a given patient.

Experiments in mice and people find that probiotic supplements don’t consistently change the composition of the gut microbiome, and may have adverse effects after antibiotics.

Four years after taking a probiotic and peanut protein for 18 months, two-thirds of children in a small clinical trial can eat peanuts with no health issues.

Genetically engineered commensal bacteria help researchers detect cancer metastases in mouse livers.