Bacterial Degradation of Gastrointestinal Mucins

Abstract

Summary 1.Quantitative stool collections were obtained from 3 male germ-free rats and 3 male conventional rats of comparable weight during the last 4 days of a 5-day diet consisting solely of 10% glucose in Ringer's solution ad libitum. The stools were homogenized and the dialyzable and nondialyzable portions of the supernatant fraction were assayed for proteins, hexoses, hexosamines, methyl pentoses, sialic acids, and blood group A, B, and H antigens. 2.The nondialyzable fraction of germfree rat stools contains a greater proportion of carbohydrates and a smaller proportion of proteins than does this fraction from conventional rat stools. 3.The average daily excretion of non-dialyzable carbohydrates was 6 to 10 times greater in the stools of germ-free rats than in the stools of conventional rats, whereas the excretion of proteins was only half again as great. The fecal excretion of dialyzable carbohydrates by the germ-free animals was also greater than by the conventional rats. A significant portion of this dialyzable carbohydrate in the germ-free rat stools was glucose, presumably unabsorbed from the diet and undegraded by intestinal bacteria. 4.ABH antigens were detected only in the nondialyzable fraction of germ-free rat stools. 5.Forty-eight hours of anaerobic incubation of rat fecal microorganisms in a medium containing the nondialyzable fraction of germ-free rat stools as the sole carbon source resulted in a 75 to 90% decrease in the carbohydrate concentration of the medium, a smaller (20%) decrease in protein concentration, and a marked decrease in the titer of blood group antigen A. 6.It is concluded that intestinal microorganisms degrade gastrointestinal mucins, particularly their carbohydrate moieties. The carbohydrate moieties may constitute a source of nutrition for intestinal bacteria.