THE MICROBIOME REVOLUTION: Companies Aim to Make Drugs from Bacteria That Live in the Gut. “It’s a jungle in there: massive populations of microbes, immune cells, and cells of the gut tissue are interacting and exchanging countless chemical and physical signals. Disruptions to this complex ecosystem, often called the microbiome, have been linked not only to gastrointestinal problems but also to metabolic, immunological, and even neurological disorders.”