Robb Craig S, Hobbs Joanne K, Pluvinage Benjamin, Reintjes Greta, Klassen Leeann, Monteith Stephanie, Giljan Greta, Amundsen Carolyn, Vickers Chelsea, Hettle Andrew G, Hills Rory, Xing Xiaohui, Montina Tony, Zandberg Wesley F, Abbott D Wade, Boraston Alisdair B
Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada.
Department of Biochemistry and Molecular Biology and Centre for Blood Research, The University of British Columbia, Vancouver, British Columbia, Canada.
Nat Chem Biol. 2022 May;18(5):501-510. doi: 10.1038/s41589-022-00983-y. Epub 2022 Mar 14.
Native porphyran is a hybrid of porphryan and agarose. As a common element of edible seaweed, this algal galactan is a frequent component of the human diet. Bacterial members of the human gut microbiota have acquired polysaccharide utilization loci (PULs) that enable the metabolism of porphyran or agarose. However, the molecular mechanisms that underlie the deconstruction and use of native porphyran remains incompletely defined. Here, we have studied two human gut bacteria, porphyranolytic Bacteroides plebeius and agarolytic Bacteroides uniformis, that target native porphyran. This reveals an exo-based cycle of porphyran depolymerization that incorporates a keystone sulfatase. In both PULs this cycle also works together with a PUL-encoded agarose depolymerizing machinery to synergistically reduce native porphyran to monosaccharides. This provides a framework for understanding the deconstruction of a hybrid algal galactan, and insight into the competitive and/or syntrophic relationship of gut microbiota members that target rare nutrients.
天然紫菜聚糖是紫菜聚糖和琼脂糖的混合物。作为可食用海藻的常见成分，这种藻类半乳聚糖是人类饮食中的常见组成部分。人类肠道微生物群的细菌成员已经获得了能够代谢紫菜聚糖或琼脂糖的多糖利用位点（PULs）。然而，天然紫菜聚糖解构和利用的分子机制仍未完全明确。在这里，我们研究了两种靶向天然紫菜聚糖的人类肠道细菌，解紫菜聚糖拟杆菌和平滑拟杆菌。这揭示了一个基于外切酶的紫菜聚糖解聚循环，其中包含一种关键硫酸酯酶。在这两个PULs中，这个循环还与PUL编码的琼脂糖解聚机制协同作用，将天然紫菜聚糖协同降解为单糖。这为理解混合藻类半乳聚糖的解构提供了一个框架，并深入了解了靶向稀有营养素的肠道微生物群成员之间的竞争和/或互养关系。
