There is a universe of bacteria in our guts that researchers and the medical field are just now beginning to come into a more comprehensive understanding of and how this "microbiome" affects everything from how well our brain functions to what kind of mood we're in. Microbes in the gut "talk" to the brain in several ways: They produce neurotransmitters (substances that carry messages back and forth to and from the brain)--including 90 percent of the body's serotonin, our "f