Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark.
National Food Institute, Technical University of Denmark, Lyngby, Denmark.
Nat Microbiol. 2018 May;3(5):570-580. doi: 10.1038/s41564-018-0132-8. Epub 2018 Apr 2.
Metabolism of dietary glycans is pivotal in shaping the human gut microbiota. However, the mechanisms that promote competition for glycans among gut commensals remain unclear. Roseburia intestinalis, an abundant butyrate-producing Firmicute, is a key degrader of the major dietary fibre xylan. Despite the association of this taxon to a healthy microbiota, insight is lacking into its glycan utilization machinery. Here, we investigate the apparatus that confers R. intestinalis growth on different xylans. R. intestinalis displays a large cell-attached modular xylanase that promotes multivalent and dynamic association to xylan via four xylan-binding modules. This xylanase operates in concert with an ATP-binding cassette transporter to mediate breakdown and selective internalization of xylan fragments. The transport protein of R. intestinalis prefers oligomers of 4-5 xylosyl units, whereas the counterpart from a model xylan-degrading Bacteroides commensal targets larger ligands. Although R. intestinalis and the Bacteroides competitor co-grew in a mixed culture on xylan, R. intestinalis dominated on the preferred transport substrate xylotetraose. These findings highlight the differentiation of capture and transport preferences as a possible strategy to facilitate co-growth on abundant dietary fibres and may offer a unique route to manipulate the microbiota based on glycan transport preferences in therapeutic interventions to boost distinct taxa.
膳食糖的代谢在塑造人类肠道微生物群方面起着关键作用。然而，促进肠道共生菌竞争糖的机制仍不清楚。Roseburia intestinalis 是一种丰富的、产生丁酸盐的厚壁菌，是主要膳食纤维木聚糖的主要降解菌。尽管该分类群与健康的微生物群有关，但对其聚糖利用机制仍缺乏了解。在这里，我们研究了赋予 R. intestinalis 生长不同木聚糖能力的装置。R. intestinalis 显示出一种大型的细胞附着的模块化木聚糖酶，通过四个木聚糖结合模块促进多价和动态与木聚糖的结合。这种木聚糖酶与 ATP 结合盒转运蛋白协同作用，介导木聚糖片段的分解和选择性内化。R. intestinalis 的转运蛋白更喜欢 4-5 个木糖基单元的低聚物，而来自模型木聚糖降解拟杆菌共生体的对应物则靶向更大的配体。尽管 R. intestinalis 和拟杆菌竞争者在木聚糖上的混合培养中共同生长，但 R. intestinalis 在首选的转运底物木四糖上占主导地位。这些发现强调了捕获和转运偏好的分化可能是一种促进在丰富的膳食纤维上共同生长的策略，并可能为基于聚糖转运偏好的治疗干预提供一种独特的途径来促进特定分类群的生长。
