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）：居住在人类远端肠道的微生物群落提高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多种策略来代谢许多来自饮食和宿主的聚糖，这些聚糖淹没了它们的栖息地。拟杆菌门是肠道细菌中两个数量占优势的门之一，其成员拥有一系列同源外膜蛋白系统（Sus 样系统），可结合聚糖并通过酶促降解聚糖。这些物种在其细胞表面普遍产生多种荚膜多糖（CPS）。尽管一些研究指出这些胶囊的作用是逃避或操纵宿主免疫，但其作用仍不清楚。我们已经证明，丰富的人类肠道共生体多形拟杆菌 (Bt) 中的 CPS 表达与一些参与降解宿主衍生粘液聚糖的 Sus 样系统的表达相协调。此外，与生活在富含植物聚糖饮食的小鼠中的 Bt 相比，在限生小鼠肠道中被迫完全依赖宿主聚糖的 Bt 群体表达不同的 CPS。这些观察结果得出我们的中心假设，即 Bt 协调其表面 CPS 结构的表达与其分解代谢的特定聚糖，因为每个胶囊的生化特性与特定的聚糖营养物子集相容。多种特性可能导致这种现象，包括增加外源聚糖与某些 CPS 结构的混溶性或将降解聚糖衍生的糖回收到新胶囊中。 Bt 型菌株 (VPI-5482) 编码八个不同的基因簇以产生 CPS。我们的初步数据表明，该菌株 CPS 基因表达的改变降低了其在粘液 O-聚糖等某些底物上的生长速度，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，我们构建了一系列八个突变体，每个突变体除了一个 CPS 基因座外均存在缺陷。每个菌株仅产生一个表面胶囊，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，结合包含 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，这些菌株提供了分离每种 CPS 聚合物并探索其糖化学结构的独特机会，我们将与普渡大学的 Bradley Reuhs 博士合作进行这项工作。最后，我们将把这八个菌株的核苷酸特征标记变体引入无菌小鼠中，以测量它们在体内相互竞争的能力。我们将控制喂给小鼠的膳食聚糖的类型和丰度，并检查每种菌株在粘液层的定植，我们假设这两个变量将影响单个 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且具有生理活性的群落的日益了解中。 公共健康相关性：人类肠道中定植的数百种细菌对于膳食碳水化合物的消化至关重要，并且还在其细胞表面产生大量荚膜多糖，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与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。