A discrete genetic locus confers xyloglucan metabolism in select human gut Bacteroidetes.
A discrete genetic locus confers xyloglucan metabolism in select human gut Bacteroidetes.
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均衡的人类饮食包括从各种水果和蔬菜的细胞壁中大量摄入非淀粉多糖，统称为“膳食纤维”。由于缺乏由人类基因组编码的消化酶，我们从膳食纤维中获取能量的能力取决于位于我们远端肠道中的大量微生物群落对复杂碳水化合物的糖化和发酵。特别地，木葡聚糖（XyGs）是高度分支的植物细胞壁多糖的普遍存在的家族，其在人肠道中的降解机制和随后在营养中的重要性迄今为止是未知的。在这里，我们证明了一个单一的，复杂的基因位点在卵形拟杆菌赋予木葡聚糖催化剂在这个共同的结肠共生体。通过有针对性的基因破坏，所有预测的糖苷水解酶和碳水化合物结合蛋白的生化分析，以及先锋内切木葡聚糖酶的三维结构测定，我们揭示了XyGs水解为单糖组分以进一步代谢的分子机制。我们还观察到，邻位木葡聚糖利用位点（XyGULs）作为拟杆菌属中木葡聚糖催化剂的遗传标记，XyGULs仅限于有限数量的遗传多样性菌株，并且XyGULs在调查的人类宏基因组中普遍存在。我们的研究结果表明，即使是高度丰富的膳食纤维成分的代谢可能是由小生境物种介导的，这对人类饮食，营养和健康背景下的肠道共生种群生态学具有直接的基本和实际意义。
A well-balanced human diet includes a significant intake of non-starch polysaccharides, collectively termed “dietary fibre,” from the cell walls of diverse fruits and vegetables. Due to a paucity of alimentary enzymes encoded by the human genome, our ability to derive energy from dietary fibre depends on saccharification and fermentation of complex carbohydrates by the massive microbial community residing in our distal gut. The xyloglucans (XyGs), in particular, are a ubiquitous family of highly branched plant cell wall polysaccharides whose mechanism(s) of degradation in the human gut and consequent importance in nutrition was heretofore unknown. Here, we demonstrate that a single, complex gene locus in Bacteroides ovatus confers xyloglucan catabolism in this common colonic symbiont. Through targeted gene disruption, biochemical analysis of all predicted glycoside hydrolases and carbohydrate-binding proteins, and three-dimensional structural determination of the vanguard endo-xyloglucanase, we reveal the molecular mechanisms through which XyGs are hydrolysed to component monosaccharides for further metabolism. We also observe that orthologous xyloglucan utilization loci (XyGULs) serve as genetic markers of xyloglucan catabolism in Bacteroidetes, that XyGULs are restricted to a limited number of phylogenetically diverse strains, and that XyGULs are ubiquitous in surveyed human metagenomes. Our findings reveal that the metabolism of even highly abundant components of dietary fibre may be mediated by niche species, which has immediate fundamental and practical implications for gut symbiont population ecology in the context of human diet, nutrition and health.
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聚糖代谢如何塑造人类肠道微生物群。
DOI：
10.1038/nrmicro2746
发表时间：
2012-04-11
期刊：
Nature reviews. Microbiology
影响因子：
--
作者：
通讯作者：
--
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
2.3
作者：
Hartemink, R;VanLaere, KMJ;Rombouts, FM
通讯作者：
Rombouts, FM
影响因子：
3.1
作者：
Hoffman, M;Jia, ZH;York, WS
通讯作者：
York, WS
影响因子：
3.4
作者：
Aspeborg H;Coutinho PM;Wang Y;Brumer H 3rd;Henrissat B
通讯作者：
Henrissat B