Bacteria and gastrointestinal secretion and motility.

The composition of the flora of the large bowel is extremely complex, as are the combination of factors involved in its control. As would be expected, although the host affects the gut flora, equally the gut flora affects the host. One of the results of this interplay is that subtle changes can lead to a marked effect on the host resulting in disease. It is now well established that bacteria can alter both secretion and motility of the gastrointestinal tract. However the effect on both of these functions has been best studied in the small bowel, this being especially true for studies on motility. In order to appreciate fully the complexity of the situation and to understand the activities of the flora that can modify gut function a brief overview of the flora of the gastrointestinal tract in health and disease and the factors involved in its regulation will be given. This will be followed by a general description of the effects of this flora on the gut, and a specific account of how large bowel motility and secretion can be altered.