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PUL0467 |
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18996345, Cell Host Microbe. 2008 Nov 13;4(5):447-57. doi: 10.1016/j.chom.2008.09.007. |
| | Mucosal glycan foraging enhances fitness and transmission of a saccharolytic human gut bacterial symbiont. |
| | Martens EC, Chiang HC, Gordon JI |
| | The distal human gut is a microbial bioreactor that digests complex carbohydrates. The strategies evolved by gut microbes to sense and process diverse glycans have important implications for the assembly and operation of this ecosystem. The human gut-derived bacterium Bacteroides thetaiotaomicron forages on both host and dietary glycans. Its ability to target these substrates resides in 88 polysaccharide utilization loci (PULs), encompassing 18% of its genome. Whole genome transcriptional profiling and genetic tests were used to define the mechanisms underlying host glycan foraging in vivo and in vitro. PULs that target all major classes of host glycans were identified. However, mucin O-glycans are the principal host substrate foraged in vivo. Simultaneous deletion of five genes encoding ECF-sigma transcription factors, which activate mucin O-glycan utilization, produces defects in bacterial persistence in the gut and in mother-to-offspring transmission. Thus, PUL-mediated glycan catabolism is an important component in gut colonization and may impact microbiota ecology. |
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31160824, Nat Microbiol. 2019 Sep;4(9):1571-1581. doi: 10.1038/s41564-019-0466-x. Epub 2019 Jun 3. |
| | Complex N-glycan breakdown by gut Bacteroides involves an extensive enzymatic apparatus encoded by multiple co-regulated genetic loci. |
| | Briliute J, Urbanowicz PA, Luis AS, Basle A, Paterson N, Rebello O, Hendel J, Ndeh DA, Lowe EC, Martens EC, Spencer DIR, Bolam DN, Crouch LI |
| | Glycans are the major carbon sources available to the human colonic microbiota. Numerous N-glycosylated proteins are found in the human gut, from both dietary and host sources, including immunoglobulins such as IgA that are secreted into the intestine at high levels. Here, we show that many mutualistic gut Bacteroides spp. have the capacity to utilize complex N-glycans (CNGs) as nutrients, including those from immunoglobulins. Detailed mechanistic studies using transcriptomic, biochemical, structural and genetic techniques reveal the pathway employed by Bacteroides thetaiotaomicron (Bt) for CNG degradation. The breakdown process involves an extensive enzymatic apparatus encoded by multiple non-adjacent loci and comprises 19 different carbohydrate-active enzymes from different families, including a CNG-specific endo-glycosidase activity. Furthermore, CNG degradation involves the activity of carbohydrate-active enzymes that have previously been implicated in the degradation of other classes of glycan. This complex and diverse apparatus provides Bt with the capacity to access the myriad different structural variants of CNGs likely to be found in the intestinal niche. |
