Bacterial interactions in the small intestine and their contribution to host nutrient uptake

Bacteria and other microbes in the upper gastrointestinal tract, stomach and duodenum, have often been considered as almost indifferent, or even non-existent. However, the microbiology of these areas is the clue for understanding the entire microbial ecosystems of the alimentary tract. The low numbers of the microbes especially in the duodenum does not imply that the microflora and its composition there would be less important or insignificant. As a matter of fact, the situation is quite the contrary. In this chapter the essential importance of the duodenal microflora for the formation of all intestinal microbial community is elucidated. In these small intestinal environments also the highest amounts of nutrients are taken up by the body. Already at 1927 Kendall and coworkers made a statement: "The duodenal tract of normal individual is an important part of the alimentary tract, not only it receives secretions from the neighboring glandular organs, but also because it is the place of the initial development of that vast column of bacteria, numbering some thirty millions, which is excreted daily in the fecal mass. "These huge masses of microscopic organisms essentially contribute on the nutrient absorption in the small intestines.