[The metabolic processes of intestinal flora]

Man is habitat of 10(14)-10(15) bacteria, most of them colonizing the digestive tract, mainly the large intestine. Here microbial metabolic processes are going on like in a black box. Their quality, quantity, dynamics and effects on the host are discernible only in fragments or from their net effect. Almost all organic compounds and nutrients, fiber, xenobiotics, digestive secretions and desquamated epithelial cells of the host enter into macroorganismic/microorganismic metabolic chains and processes, which are not known or measurable in detail. Examples are given for the metabolization of nutrients, esp. amino acids. Some information is concerned with morphological, physiological, biochemical immunological and pathological effects of the gastrointestinal flora, discernible from experiments with gnotobiotic animals. Microbial influences upon basic life processes of the host are described in a few examples.