BY-DONNA GATES FOR SELINA NATURALLY® The inner ecosystem is a civilization that lives in the small and large intestine. In a healthy body, this civilization consists mostly of neutral bacteria. Fifteen to twenty percent of the civilization is considered good bacteria, these are bacteria doing important things for the digestion of foods. Also, even in a healthy body, there are a small number of “bad” bacteria which do not throw the system out of balance. There have been over 400 different microorganisms identified that could live in the gut. Many of them, as I mentioned, are neutral.