Prebiotics are non-digestible (by the host) food ingredients that have a beneficial effect through their selective metabolism in the intestinal tract. Key to this is the specificity of microbial changes. The present paper reviews the concept in terms of three criteria: (a) resistance to gastric acidity, hydrolysis by mammalian enzymes and gastrointestinal absorption; (b) fermentation by intestinal microflora; (c) selective stimulation of the growth and/or activity of intestinal bacteria associated with health and wellbeing. The conclusion is that prebiotics that currently fulfil these three criteria are fructo-oligosaccharides, galacto-oligosaccharides and lactulose, although promise does exist with several other dietary carbohydrates. Given the range of food vehicles that may be fortified by prebiotics, their ability to confer positive microflora changes and the health aspects that may accrue, it is important that robust technologies to assay functionality are used. This would include a molecular-based approach to determine flora changes. The future use of prebiotics may allow species-level changes in the microbiota, an extrapolation into genera other than the bifidobacteria and lactobacilli, and allow preferential use in disease-prone areas of the body.

/pdf/dietary-modulation-of-the-human-colonic-microbiota-updating-tz2ksl8b3e.pdf

Dietary modulation of the human colonic microbiota: updating the concept of prebiotics

https://orbilu.uni.lu/bitstream/10993/37916/1/Desai%282016%29Cell.pdf

A Dietary Fiber-Deprived Gut Microbiota Degrades the Colonic Mucus Barrier and Enhances Pathogen Susceptibility

Humans and other mammals are colonized by a vast, complex, and dynamic consortium of microorganisms. One evolutionary driving force for maintaining this metabolically active microbial society is to salvage energy from nutrients, particularly carbohydrates, that are otherwise nondigestible by the host. Much of our understanding of the molecular mechanisms by which members of the intestinal microbiota degrade complex polysaccharides comes from studies of Bacteroides thetaiotaomicron, a prominent and genetically manipulatable component of the normal human and mouse gut. Colonization of germ-free mice with B. thetaiotaomicron has shown how this anaerobe modifies many aspects of intestinal cellular differentiation/gene expression to benefit both host and microbe. These and other studies underscore the importance of understanding precisely how nutrient metabolism serves to establish and sustain symbiotic relationships between mammals and their bacterial partners.

How host-microbial interactions shape the nutrient environment of the mammalian intestine

The diversity of mucin-degrading bacteria in the human intestine was investigated by combining culture and 16S rRNA-dependent approaches. A dominant bacterium, strain MucT, was isolated by dilution to extinction of faeces in anaerobic medium containing gastric mucin as the sole carbon and nitrogen source. A pure culture was obtained using the anaerobic soft agar technique. Strain MucT was a Gram-negative, strictly anaerobic, non-motile, non-spore-forming, oval-shaped bacterium that could grow singly and in pairs. When grown on mucin medium, cells produced a capsule and were found to aggregate. Strain MucT could grow on a limited number of sugars, including N-acetylglucosamine, N-acetylgalactosamine and glucose, but only when a protein source was provided and with a lower growth rate and final density than on mucin. The G + C content of DNA from strain MucT was 47.6 mol%. 16S rRNA gene sequence analysis revealed that the isolate was part of the division Verrucomicrobia. The closest described relative of strain MucT was Verrucomicrobium spinosum (92 % sequence similarity). Remarkably, the 16S rRNA gene sequence of strain MucT showed 99 % similarity to three uncultured colonic bacteria. According to the data obtained in this work, strain MucT represents a novel bacterium belonging to a new genus in subdivision 1 of the Verrucomicrobia; the name Akkermansia muciniphila gen. nov., sp. nov. is proposed; the type strain is MucT (= ATCC BAA-835T = CIP 107961T).

/pdf/akkermansia-muciniphila-gen-nov-sp-nov-a-human-intestinal-icf8ckwfxn.pdf

Akkermansia muciniphila gen. nov., sp. nov., a human intestinal mucin-degrading bacterium.

The control and consequences of bacterial fermentation in the human colon.

Recent work indicates that subpopulations of human fecal bacteria, averaging approximately 1% of the total viable fecal flora, degrade the oligosaccharide side chains of hog gastric mucin, which structurally resembles human epithelial mucins. Here we report studies to determine whether degradation of mucin oligosaccharides is related to glycosidase production by bacteria growing in anaerobic fecal cultures. Triplicate cultures containing hog gastric mucin were inoculated with serially diluted feces from each of seven healthy subjects. When the stationary growth phase was attained, mucin oligosaccharide degradation and both cell-bound and extracellular activities of four glycosidases were measured in each culture. Cell-bound beta-d-galactosidase, beta-N-acetylglucosaminidase, and sialidase were present in bacteria growing at all levels of fecal inocula, including 10(-11) g. In contrast, extracellular activities were present in every culture inoculated with 10(-4)-10(-7) g feces, but were diminished or absent in cultures inoculated with 10(-8)-10(-11) g feces. Bacterial autolysis was an unlikely cause of extracellular glycosidase activity, since p-nitrophenyl-alpha-l-fucosidase remained cell bound in cultures at every level of fecal inoculum. Degradation of mucin oligosaccharides was associated with extracellular, but not with cell-bound beta-d-galactosidase, beta-N-acetylglucosaminidase, and sialidase. Among the seven subjects, the estimated most probable numbers (MPN) of fecal bacteria producing extracellular beta-d-galactosidase, beta-N-acetylglucosaminidase, and sialidase ranged from 10(6)-10(10)/g dry fecal wt, were comparable to the MPN of mucin-degrading bacteria, and were significantly smaller than the MPN of total fecal bacteria. We interpret these findings as evidence for the existence of bacterial subpopulations in the normal fecal flora that produce extracellular glycosidases, and that these subpopulations have a major role in degrading the complex oligosaccharides of mucin in the gut lumen.

/pdf/mucin-degradation-in-human-colon-ecosystems-evidence-for-the-uvck9x0xhw.pdf

Mucin degradation in human colon ecosystems. Evidence for the existence and role of bacterial subpopulations producing glycosidases as extracellular enzymes.

Mucin degradation in human colon ecosystems. Fecal population densities of mucin-degrading bacteria estimated by a "most probable number" method.

Bacterial degradation of gastrointestinal mucins. I. Comparison of mucus constituents in the stools of germ-free and conventional rats.

THERE is increasing evidence of an association between the ABO blood groups and certain diseases of the upper gastrointestinal tract.1 , 2 This association has been noted with gastric carcinoma and with the gastric atrophy of pernicious anemia, both of which appear to occur more frequently among persons of blood group A than among those of blood group O. As part of studies of the relation between gastric atrophy and gastric carcinoma, we have determined the distribution of ABO blood groups for 158 patients with pernicious anemia, 337 patients with gastric carcinoma and 32 patients with pernicious anemia in whom gastric carcinoma . . .

Distribution of Abo Blood Groups in Patients with Pernicious Anemia, Gastric Carcinoma and Gastric Carcinoma Associated with Pernicious Anemia

https://www.gastrojournal.org/article/0016-5085(81)90502-3/pdf

Lansing C. Hoskins

Papers

Mucin degradation in human colon ecosystems. Evidence for the existence and role of bacterial subpopulations producing glycosidases as extracellular enzymes.

Mucin degradation in human colon ecosystems. Fecal population densities of mucin-degrading bacteria estimated by a "most probable number" method.

Bacterial degradation of gastrointestinal mucins. I. Comparison of mucus constituents in the stools of germ-free and conventional rats.

Distribution of Abo Blood Groups in Patients with Pernicious Anemia, Gastric Carcinoma and Gastric Carcinoma Associated with Pernicious Anemia

Mucin degradation in human colon ecosystems. Degradation of hog gastric mucin by fecal extracts and fecal cultures