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      Microbial Metabolic Networks at the Mucus Layer Lead to Diet-Independent Butyrate and Vitamin B 12 Production by Intestinal Symbionts

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          Akkermansia muciniphila has evolved to specialize in the degradation and utilization of host mucus, which it may use as the sole source of carbon and nitrogen. Mucus degradation and fermentation by A. muciniphila are known to result in the liberation of oligosaccharides and subsequent production of acetate, which becomes directly available to microorganisms in the vicinity of the intestinal mucosa. Coculturing experiments of A. muciniphila with non-mucus-degrading butyrate-producing bacteria Anaerostipes caccae, Eubacterium hallii, and Faecalibacterium prausnitzii resulted in syntrophic growth and production of butyrate. In addition, we demonstrate that the production of pseudovitamin B 12 by E. hallii results in production of propionate by A. muciniphila, which suggests that this syntrophy is indeed bidirectional. These data are proof of concept for syntrophic and other symbiotic microbe-microbe interactions at the intestinal mucosal interface. The observed metabolic interactions between A. muciniphila and butyrogenic bacterial taxa support the existence of colonic vitamin and butyrate production pathways that are dependent on host glycan production and independent of dietary carbohydrates. We infer that the intestinal symbiont A. muciniphila can indirectly stimulate intestinal butyrate levels in the vicinity of the intestinal epithelial cells with potential health benefits to the host.


          The intestinal microbiota is said to be a stable ecosystem where many networks between microorganisms are formed. Here we present a proof of principle study of microbial interaction at the intestinal mucus layer. We show that indigestible oligosaccharide chains within mucus become available for a broad range of intestinal microbes after degradation and liberation of sugars by the species Akkermansia muciniphila. This leads to the microbial synthesis of vitamin B 12, 1,2-propanediol, propionate, and butyrate, which are beneficial to the microbial ecosystem and host epithelial cells.

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          Most cited references 28

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          How glycan metabolism shapes the human gut microbiota.

          Symbiotic microorganisms that reside in the human intestine are adept at foraging glycans and polysaccharides, including those in dietary plants (starch, hemicellulose and pectin), animal-derived cartilage and tissue (glycosaminoglycans and N-linked glycans), and host mucus (O-linked glycans). Fluctuations in the abundance of dietary and endogenous glycans, combined with the immense chemical variation among these molecules, create a dynamic and heterogeneous environment in which gut microorganisms proliferate. In this Review, we describe how glycans shape the composition of the gut microbiota over various periods of time, the mechanisms by which individual microorganisms degrade these glycans, and potential opportunities to intentionally influence this ecosystem for better health and nutrition.
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            Effect of inulin on the human gut microbiota: stimulation of Bifidobacterium adolescentis and Faecalibacterium prausnitzii.

            Prebiotics are food ingredients that improve health by modulating the colonic microbiota. The bifidogenic effect of the prebiotic inulin is well established; however, it remains unclear which species of Bifidobacterium are stimulated in vivo and whether bacterial groups other than lactic acid bacteria are affected by inulin consumption. Changes in the faecal microbiota composition were examined by real-time PCR in twelve human volunteers after ingestion of inulin (10 g/d) for a 16-d period in comparison with a control period without any supplement intake. The prevalence of most bacterial groups examined did not change after inulin intake, although the low G+C % Gram-positive species Faecalibacterium prausnitzii exhibited a significant increase (10.3% for control period v. 14.5% during inulin intake, P=0.019). The composition of the genus Bifidobacterium was studied in four of the volunteers by clone library analysis. Between three and five Bifidobacterium spp. were found in each volunteer. Bifidobacterium adolescentis and Bifidobacterium longum were present in all volunteers, and Bifidobacterium pseudocatenulatum, Bifidobacterium animalis, Bifidobacterium bifidum and Bifidobacterium dentium were also detected. Real-time PCR was employed to quantify the four most prevalent Bifidobacterium spp., B. adolescentis, B. longum, B. pseudocatenulatum and B. bifidum, in ten volunteers carrying detectable levels of bifidobacteria. B. adolescentis showed the strongest response to inulin consumption, increasing from 0.89 to 3.9% of the total microbiota (P=0.001). B. bifidum was increased from 0.22 to 0.63% (P<0.001) for the five volunteers for whom this species was present.
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              Microbes inside--from diversity to function: the case of Akkermansia.

               W Vos,  Clara Belzer (2012)
              The human intestinal tract is colonized by a myriad of microbes that have developed intimate interactions with the host. In healthy individuals, this complex ecosystem remains stable and resilient to stressors. There is significant attention on the understanding of the composition and function of this intestinal microbiota in health and disease. Current developments in metaomics and systems biology approaches allow to probe the functional potential and activity of the intestinal microbiota. However, all these approaches inherently suffer from the fact that the information on macromolecules (DNA, RNA and protein) is collected at the ecosystem level. Similarly, all physiological and other information collected from isolated strains relates to pure cultures grown in vitro or in gnotobiotic systems. It is essential to integrate these two worlds of predominantly chemistry and biology by linking the molecules to the cells. Here, we will address the integration of omics- and culture-based approaches with the complexity of the human intestinal microbiota in mind and the mucus-degrading bacteria Akkermansia spp. as a paradigm.

                Author and article information

                Role: Editor
                American Society for Microbiology (1752 N St., N.W., Washington, DC )
                19 September 2017
                Sep-Oct 2017
                : 8
                : 5
                [a ]Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
                [b ]Department of Food and Environmental Sciences, University of Helsinki, Helsinki, Finland
                [c ]Nutricia Research, Utrecht, The Netherlands
                [d ]RPU Immunobiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
                Max Planck Institute for Marine Microbiology
                Author notes
                Address correspondence to Clara Belzer, clara.belzer@ 123456wur.nl .
                Copyright © 2017 Belzer et al.

                This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

                Page count
                supplementary-material: 2, Figures: 5, Tables: 3, Equations: 0, References: 59, Pages: 14, Words: 7920
                Funded by: EC | European Research Council (ERC) https://doi.org/10.13039/501100000781
                Award ID: 250172
                Award Recipient : Clara Belzer Award Recipient : Steven Aalvink Award Recipient : Willem M. de Vos
                Funded by: Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) https://doi.org/10.13039/501100003246
                Award ID: 024.002.002
                Award Recipient : Clara Belzer Award Recipient : Steven Aalvink Award Recipient : Willem M. de Vos
                Research Article
                Custom metadata
                September/October 2017

                Life sciences

                akkermansia muciniphila, anaerobes, butyrate, cross-feeding, intestine, microbiome, mucus, syntrophy


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