Lansing C. Hoskins

Bacterial Degradation of Gastrointestinal Mucins: I. Comparison of mucus constituents in the stools of germ-free and conventional rats

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 Ringers 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.

Bacterial degradation of gastrointestinal mucins. II. Bacterial origin of fecal ABH(O) blood group antigen-destroying enzymes.

Summary The source of ABO blood group antigendestroying enzymes in mammalian stools was investigated. 1.The stools of conventional rats but not those of germ-free rats contained blood group-destroying (BGD) enzyme activity. 2.BGD enzyme activity was present in fecal homogenates of conventional rats and developed in liquid anaerobic bacterial cultures of stool and cecal contents during their incubation at 37 C. Homogenates of stomach, pancreas, liver, small intestinal mucosa, and mucosa of cecum and colon possessed no demonstrable BGD enzyme activity. 3.Jejunal mucosa from one human subject whose stools consistently contain BGD enzyme activity had no demonstrable BGD enzyme activity. It is concluded that fecal blood groupdestroying enzyme activity arises from intestinal microorganisms.