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（由申请方提供）：栖息在人体远端肠道中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。这个群落中的细菌已经进化出几种策略来代谢淹没其栖息地的许多饮食和宿主来源的聚糖。拟杆菌属（Bacteroidetes）是肠道细菌的两个数量上占优势的门之一，其成员具有一系列结合并酶促降解聚糖的同源外膜蛋白系统（Sus-like系统）。这些物种普遍在其细胞表面上产生多个荚膜多糖（CPS）。这些胶囊的作用仍然不确定，尽管一些研究指出逃避或操纵宿主免疫。我们已经表明，CPS在丰富的人类肠道共生体多形拟杆菌（Bt）中的表达与参与降解宿主来源的粘液聚糖的一些Sus样系统的表达相协调。此外，被迫完全依赖于在gnotobiotic小鼠肠道中的宿主聚糖的Bt种群相对于在喂食富含植物聚糖的饮食的小鼠中生活的Bt表达不同的CPS。这些观察结果导致我们的中心假设，Bt协调其表面CPS结构的表达与特定的聚糖，它是分解代谢，因为每个单独的胶囊的生化特性是兼容的聚糖营养素的特定子集。几种性质可能导致这种现象，包括具有某些CPS结构的外源聚糖的可溶解性增加或降解聚糖衍生的糖再循环到新的胶囊中。Bt型菌株（VPI-5482）编码产生CPS的8个不同基因簇。我们的初步数据表明，这种菌株在CPS基因表达上的改变降低了其在某些底物（如粘液O-聚糖）上的生长速率，同时使其在其他底物上与野生型相同或更快。为了扩展这些发现，我们构建了一系列的八个突变体，每个突变体除了一个CPS位点之外都有缺陷。每种菌株只产生一个单一的表面胶囊，使我们能够在体外和体内分离其对不同聚糖生长的贡献。我们将使用这八个菌株，结合含有47种不同碳水化合物的定制生长阵列，来测量单个胶囊对体外Bt聚糖代谢的影响。此外，这些菌株提供了一个独特的机会，以分离每个CPS聚合物和探索其糖化学结构，我们将执行合作博士布拉德利普渡大学。最后，我们将把这八个菌株的核苷酸特征标记的变体引入无菌小鼠中，以测量它们在体内相互竞争的能力。我们将操纵喂食给小鼠的膳食聚糖的类型和丰度，并检查每种菌株对粘液层的定植，这两个变量我们假设将影响个体CPS表达菌株的适应性。总之，在拟议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和生理活性群落的不断增长的理解中。 公共卫生关系：定植在人体肠道中的数百种细菌对于消化膳食碳水化合物是必不可少的，并且还在其细胞表面上产生许多荚膜多糖，以保护它们免受宿主免疫反应的影响。我们将测量细菌细胞表面胶囊和肠道细菌帮助我们消化的碳水化合物之间的相互作用。这些发现将揭示通常生活在我们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降解保护性粘液屏障中所含的聚糖来影响人类健康。