The role of polysaccharide surface capsules in Bacteroides glycan degradation

多糖表面胶囊在拟杆菌聚糖降解中的作用

• 批准号: 8354382
• 负责人: Eric C Martens
• 金额: $ 8.06万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-25 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8354382
• 关键词: Affect; Animals; Anti-Inflammatory Agents; Anti-inflammatory; Bacteria; Bacteroides; Bacteroides fragilis; Bacteroides thetaiotaomicron; Bacteroidetes; Binding; Biochemical; Biochemistry; Calories; Carbohydrates; Catabolism; Cell surface; Collaborations; Communities; Complex; Custom; Data; Diet; Dietary Carbohydrates; Dietary Polysaccharide; Digestion; Disease; Distal; Environment; Fermentation; Fostering; Gene Cluster; Gene Expression; Genes; Genetic Transcription; Gnotobiotic; Goals; Growth; Habitats; Health; Human; Immune response; Immunity; In Vitro; Individual; Inflammatory Bowel Diseases; Intestines; Knowledge; Lead; Life; Light; Link; Measures; Membrane Proteins; Metabolism; Metagenomics; Methods; Monosaccharides; Mucous body substance; Mus; Nucleotides; Nutrient; Outcome; Pathway interactions; Phylogenetic Analysis; Physiology; Plants; Play; Polymers; Polysaccharides; Population; Production; Property; Recycling; Relative (related person); Reporting; Role; Sampling; Series; Shapes; Source; Structure; Surface; System; Taxon; Testing; Tissues; Universities; Variant; Work; animal tissue; base; capsule; feeding; fitness; in vivo; insight; member; microbial; microbial community; mutant; novel; research study; response; sugar

DESCRIPTION (provided by applicant): The microbial community that inhabits the human distal gut increases our ability to digest complex carbohydrates (glycans). Bacteria in this community have evolved several strategies to metabolize the many diet- and host-derived glycans that inundate their habitat. Members of the Bacteroidetes, one of two numerically dominant phyla of gut bacteria, possess a series of homologous outer membrane protein systems (Sus-like systems) that bind and enzymatically degrade glycans. These species ubiquitously produce multiple capsular polysaccharides (CPS) on their cell surfaces. The role of these capsules remains undefined, although some studies point to evasion or manipulation of host immunity. We have shown that CPS expression in the abundant human gut symbiont Bacteroides thetaiotaomicron (Bt) is coordinated with expression of some Sus- like systems involved in degrading host-derived mucus glycans. Moreover, Bt populations that are forced to rely exclusively on host glycans in the intestines of gnotobiotic mice express different CPS relative to Bt living in mice fed a diet rich in plant glycans. These observations lead to our central hypothesis that Bt coordinates expression of its surface CPS structures with the particular glycan that it is catabolizing because the biochemical properties of each individual capsule are compatible with a specific subset of glycan nutrients. Several properties could contribute to this phenomenon, including increased miscibility of exogenous glycans with some CPS structures or recycling of sugars derived from degraded glycans into new capsules. The Bt type strain (VPI-5482) encodes eight different gene clusters for producing CPS. Our preliminary data suggest that alterations in CPS gene expression by this strain decrease its growth rate on some substrates such as mucus O-glycans, while rendering it identical to or faster than wild-type on others. To extend these findings, we have constructed a series of eight mutants that are each deficient in all but one CPS locus. Each strain produces only a single surface capsule, allowing us to isolate its contribution to growth on different glycans in vitro and in vivo. We wil use these eight strains, in conjunction with a custom growth array containing 47 different carbohydrates, to measure the effect of individual capsules on Bt glycan metabolism in vitro. In addition, these strains provide a unique opportunity to isolate each CPS polymer and explore its glycochemical structure, which we will perform in collaboration Dr. Bradley Reuhs from Purdue University. Finally, we will introduce nucleotide signature-tagged variants of these eight strains into germfree mice to measure their ability to compete against each other in vivo. We will manipulate the type and abundance of dietary glycans fed to mice, and examine colonization of the mucus layer by each strain, as two variables that we hypothesize will influence the fitness of individual CPS-expressing strains. Together, the data gathered in the proposed experiments will allow us to integrate the role of variable CPS expression into a growing understanding of how bacteria assemble into a complex and physiologically active community in the human intestinal tract. PUBLIC HEALTH RELEVANCE: The hundreds of bacterial species that colonize the human intestinal tract are essential for the digestion of dietary carbohydrates and also create numerous capsular polysaccharides on their cell surface that protect them from host immune responses. We will measure the interactions between bacterial cell surface capsules and the carbohydrates that intestinal bacterial help us to digest. The findings will shed light on how the many related bacteria that normally live in our intestine influence human health by assisting in carbohydrate digestion or, in some cases, degrading glycans contained in the protective mucus barrier.

描述（由申请人提供）：居住在人类肠道的微生物群落增加了我们消化复杂碳水化合物（聚糖）的能力。这个社区中的细菌已经发展出了几种策略，以代谢淹没其栖息地的众多饮食和宿主衍生的聚糖。细菌植物的成员是肠道细菌的两个数值主要门之一，具有一系列同源外膜蛋白系统（SUS样系统），它们结合和酶促降解聚糖。这些物种普遍存在在其细胞表面产生多种囊多糖（CPS）。这些胶囊的作用仍然不确定，尽管一些研究表明逃避或操纵宿主免疫。我们已经表明，在丰富的人类肠道共生型细菌中的CPs表达与某些与降解宿主衍生的粘液聚糖有关的SUSS的表达进行了协调。此外，被迫仅依靠gnotobiotic小鼠肠道中的宿主聚糖的BT种群相对于生活在富含植物聚糖的饮食的小鼠中表达了不同的CPS。这些观察结果导致了我们的中心假设，即BT与特定的聚糖表达其表面CPS结构的表达是它正在分解代谢，因为每个单个胶囊的生化特性与特定的聚糖营养素的子集兼容。几种特性可能有助于这种现象，包括具有一些CPS结构的外源性聚糖的混溶性增加或从降解的聚糖中衍生成新胶囊的糖的回收。 BT型应变（VPI-5482）编码用于产生CP的八个不同的基因簇。我们的初步数据表明，通过这种菌株，CPS基因表达的改变会降低其在某些底物（例如粘液O-聚糖）上的生长速率，同时使其与其他质子相同或比野生型相同或更快。为了扩展这些发现，我们已经构建了一系列八个突变体，除一个CPS基因座外，每个突变体都缺乏。每个菌株仅产生一个表面胶囊，使我们能够在体外和体内隔离其对不同聚糖生长的贡献。我们将使用这八种菌株与包含47种不同碳水化合物的自定义生长阵列一起测量单个胶囊对体外BT糖代谢的影响。此外，这些菌株还提供了一个独特的机会，可以隔离每个CPS聚合物并探索其糖化化学结构，我们将在Purdue University的Bradley Reuhs博士合作中进行。最后，我们将将这八种菌株的核苷酸特征标记的变体引入无grgrefem小鼠，以衡量它们在体内相互竞争的能力。我们将操纵喂给小鼠的饮食类似物的类型和丰度，并通过每个菌株检查粘液层的定殖，因为我们假设的两个变量将影响单个表达CPS菌株的适应性。共同提出的实验中收集的数据将使我们能够将可变CPS表达的作用整合到对细菌如何在人类肠道中组装成复杂且生理活跃的社区的越来越多的理解。 公共卫生相关性：将人类肠道定植的数百种细菌物种对于消化饮食中的碳水化合物至关重要，并且在其细胞表面上也会产生许多囊膜多糖，以保护它们免受宿主免疫反应。我们将测量细菌细胞表面胶囊与肠道细菌有助于我们消化的碳水化合物之间的相互作用。这些发现将阐明通常生活在我们的肠道中的许多相关细菌如何通过协助碳水化合物消化或在某些情况下会降解在保护性粘液屏障中所含的聚糖。