Mechanisms of Salmonella-mediated disruption of colonization resistance in the inflamed gut

沙门氏菌介导的炎症肠道定植抵抗破坏机制

基本信息

批准号：
10595200
负责人：
Mariana Xavier Byndloss
金额：
$ 47.34万
依托单位：
VANDERBILT UNIVERSITY MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2022
资助国家：
美国
起止时间：
2022-09-19 至 2027-07-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10595200
关键词：
Affect Amino Acids Anaerobic Bacteria Aspartate Bacteria Bacteroides Bacteroides thetaiotaomicron Catabolism Citric Acid Cycle Cytolysis Data Ecosystem Enterobacteriaceae Epithelial Cells Escherichia coli Fluorescence Microscopy Fumarates Gastroenteritis Gastrointestinal tract structure Genes Genetic Transcription Germ-Free Growth In Vitro Infection Inflammation Intestines Invaded Measures Mediating Metabolic Metabolism Mus Nitrates Nutrient Oxidants Pathogenesis Pathway interactions Phase Physiology Play Production Propionates Reactive Oxygen Species Reporter Research Respiration Role Salmonella Salmonella typhimurium Source Study models Taxon Testing Type III Secretion System Pathway United States Virulence Volatile Fatty Acids Work antimicrobial colonization resistance commensal bacteria commensal microbes diarrheal disease enteric pathogen essays experimental study gut inflammation gut microbiota host microbiota in vivo innovation intestinal epithelium microbial microbiota mouse model mutant non-typhoidal Salmonella novel pathogen pathogenic bacteria resident commensals response

项目摘要

PROJECT SUMMARY Infection with non-typhoidal Salmonella is 1 of 4 most prevalent global causes of diarrheal disease. In the United States, Salmonella enterica serovar Typhimurium (S. Tm) infection results in 1.35 million illnesses annually. To infect the gastrointestinal tract, S. Tm contends with the resident commensal bacteria (gut microbiota). The gut microbiota benefits the host by limiting enteric pathogen expansion (colonization resistance), partially via the production of inhibitory metabolites such as short-chain fatty acids (SCFA) (e.g., propionate) and nutrient sequestration (e.g., amino acids). Thus, successful bacterial pathogens must possess mechanisms to survive in the competitive ecosystem of the gut. S. Tm uses a Type III secretion system (T3SS- I) to invade intestinal epithelial cells (EICs) and induce intestinal inflammation. As a result, S. Tm disrupts the host-microbiota ecosystem and overcomes microbiota-mediated colonization resistance by using inflammation- derived electron acceptors such as fumarate and nitrate for anaerobic respiration. However, the mechanisms that drive Salmonella-induced disruption of the microbial ecosystem in the gut and how this disruption affects host physiology and promotes pathogen expansion remain largely unknown. In this application, we will elucidate the mechanisms by which S. Tm-induced intestinal inflammation enables the pathogen to (i) overpower SCFA- mediated colonization resistance and (ii) gain access to microbiota-derived aspartate for anaerobic fumarate respiration. Our robust preliminary data obtained from in vitro studies and murine models demonstrate that the pathogen may use propionate metabolism to fine-tune virulence through modulation of T3SS-I expression. Our studies further reveal that S. Tm-induced inflammation causes an increase in Bacteroides-derived aspartate in the intestinal lumen and that aspartate conversion into fumarate fuels S. Tm fumarate respiration in vitro and in vivo. Our preliminary data support our central hypothesis that pathogen-induced intestinal inflammation allows S. Tm to overcome mechanisms of colonization resistance established by the microbiota by (i) downregulating invasion of EICs via catabolism of Bacteroides-derived propionate and (ii) promoting the release of aspartate by commensal Bacteroides, which S. Tm uses to outcompete commensal Enterobacteriaceae. To test this hypothesis, we will define the impact of propionate catabolism on S. Tm pathogenesis in the inflamed gut (Aim 1). Aim 2 will identify the mechanism by which intestinal inflammation promotes increased aspartate availability in the inflamed gut. In Aim 3, we will determine how aspartate enables S. Tm to overcome colonization resistance by Enterobacteriaceae, a bacterium taxon that plays a critical role in protecting the host against S. Tm infection. If successful, this research will establish critical conceptual advances in understanding how enteric pathogens exploit the gut microbiota for expansion during gastroenteritis. Expected findings will provide a deeper understanding of a novel mechanism used by this bacterial pathogen to evade the intestinal microbiota and establish infection.

项目概要非伤寒沙门氏菌感染是全球最常见的腹泻病 4 种原因之一。在美国，肠沙门氏菌鼠伤寒血清型 (S.Tm) 感染导致 135 万人患病每年。为了感染胃肠道，S.Tm 与常驻共生菌（肠道菌）进行斗争。微生物群）。肠道微生物群通过限制肠道病原体扩张（定植耐药性），部分是通过产生抑制性代谢物，例如短链脂肪酸（SCFA）（例如，丙酸盐）和养分封存（例如氨基酸）。因此，成功的细菌病原体必须具备在肠道竞争性生态系统中生存的机制。 S.Tm使用III型分泌系统（T3SS- I）侵入肠上皮细胞（EIC）并诱发肠道炎症。结果，S.Tm 扰乱了宿主微生物生态系统，并通过使用炎症克服微生物介导的定植抗性衍生的电子受体，例如用于无氧呼吸的富马酸盐和硝酸盐。然而，这些机制驱动沙门氏菌引起的肠道微生物生态系统破坏以及这种破坏如何影响宿主生理学和促进病原体扩张仍然很大程度上未知。在此应用中，我们将阐明 S.Tm 诱导的肠道炎症使病原体能够 (i) 压倒 SCFA- 的机制介导的定植抗性和（ii）获得微生物群衍生的天冬氨酸用于厌氧富马酸盐呼吸。我们从体外研究和小鼠模型中获得的可靠初步数据表明病原体可能利用丙酸代谢通过调节 T3SS-I 表达来微调毒力。我们的研究进一步表明，S. Tm 诱导的炎症会导致拟杆菌衍生的天冬氨酸增加肠腔和天冬氨酸转化为富马酸在体外和体内为 S.Tm 富马酸呼吸提供燃料体内。我们的初步数据支持我们的中心假设，即病原体诱导的肠道炎症允许 S. Tm 通过 (i) 下调来克服微生物群建立的定植抗性机制通过类杆菌衍生的丙酸盐的分解代谢入侵 EIC，以及 (ii) 通过促进天冬氨酸的释放共生拟杆菌，S. Tm 利用它来战胜共生肠杆菌科细菌。为了测试这个假设，我们将定义丙酸分解代谢对发炎肠道中 S.Tm 发病机制的影响（目的 1).目标 2 将确定肠道炎症促进天冬氨酸可用性增加的机制在发炎的肠道中。在目标 3 中，我们将确定天冬氨酸如何使 S.Tm 克服定植抗性肠杆菌科是一种细菌分类群，在保护宿主免受链球菌感染方面发挥着关键作用。如果成功，这项研究将在理解肠道病原体如何在胃肠炎期间利用肠道微生物群进行扩张。预期的发现将提供更深入的了解这种细菌病原体用来逃避肠道微生物群的新机制，以及建立感染。