Mechanisms of Microbial Competition During Salmonella Infection

沙门氏菌感染期间微生物竞争的机制

基本信息

批准号：
10600681
负责人：
Lauren Christine Radlinski
金额：
$ 6.95万
依托单位：
UNIVERSITY OF CALIFORNIA AT DAVIS
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：
2022-12-01 至 2025-11-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10600681
关键词：
Acids Amino Acids Animal Model Antibiotic Resistance Antibiotic Therapy Antibiotics Attenuated Biochemical Reaction Buffers Carboxy-Lyases Catabolism Cataloging Cell Death Communities Consumption Cytoplasm Cytosol Dietary Fiber Discipline Disease Ecosystem Engineering Enterobacteriaceae Environment Family Fermentation Glean Gnotobiotic Goals Growth Homeostasis Host Defense Hypoxia Immunocompromised Host In Vitro Individual Infection Inflammation Inflammatory Response Intestines Invaded Knowledge Large Intestine Link Mediating Metabolic Pathway Microbe Modeling Modification Mus Nutrient Nutritional Outcome Pathway interactions Patients Play Predisposition Production Protons Public Health Reaction Research Resistance Role Salmonella Salmonella enterica Salmonella infections Salmonella typhimurium Secure Supplementation Testing Toxic effect Treatment Failure Type III Secretion System Pathway Virulence Virulence Factors Volatile Fatty Acids Work acid stress antimicrobial bacterial genetics biological adaptation to stress colonization resistance commensal microbes dysbiosis enteric infection enteric pathogen gastrointestinal gastrointestinal infection gut colonization gut homeostasis high risk improved in vivo innovation intestinal epithelium metabolomics microbial microbial community microbiome microbiota microorganism mouse model novel therapeutic intervention pH Homeostasis pathogen prevent programs

项目摘要

PROJECT SUMMARY The microbiota is a critical frontline barrier that protects the host from invading microorganisms and keeps resident opportunists in check. Frank pathogens such as Salmonella enterica serovar Typhimurium (STm), however, are adept at overcoming microbiota-mediated colonization resistance to cause dysbiosis and disease. Under homeostasis, antimicrobial short-chain fatty acids (SCFAs) produced by the microbiota protect the host by restricting pathogen replication through cytosol acidification. During infection, STm uses its type III secretion systems (T3SS) to trigger an inflammatory response that depletes SCFA-producing commensals. Current paradigm holds that the depletion of SCFA-producing species is a pre-requisite for luminal STm expansion. However, using an antibiotic-naïve mouse model we have observed that STm blooms 1000-fold 3-4 days prior to the onset of overt inflammation when SCFAs are abundant and the community composition of the microbiota is undisturbed. This implies that STm employs an as-of-yet undescribed strategy to restore pH homeostasis and grow in the presence of SCFAs during gastrointestinal colonization. Our preliminary findings suggest that proton- consuming metabolic pathways, including the amino acid decarboxylases CadA and SpeF, alleviate SCFA growth inhibition in vitro and are required for full virulence in vivo, yet it is unclear whether these pathways specifically mediate growth in the presence of SCFAs within the host, or how STm secures the metabolites that fuel these pathways in the nutrient-restricted gastrointestinal environment. I hypothesize that during colonization of the gastrointestinal tract, STm uses its T3SS to obtain host-derived amino acids that fuel proton-consuming reactions and restore pH homeostasis in the presence of commensal-produced SCFAs. The objective of this application is to elucidate how STm adapts to the intestinal environment and to use this understanding to develop my own independent research program that investigates how enteric pathogens overcome intrinsic protective barriers so that we may uncover new therapeutic approaches for bolstering colonization resistance in high-risk patients. In AIM1 we will assess the contribution of proton-consuming metabolic pathways in restoring pH homeostasis and growth in the presence of SCFAs in vitro, and investigate the role these pathways play in mediating early ecosystem invasion in vivo using conventional and gnotobiotic animal models. In AIM2 we will use bacterial genetics, murine infection models, and metabolomics to determine how STm uses its virulence factors to engineer a new gastrointestinal niche that supports dysbiotic Enterobacteriaceae expansion under homeostatic conditions. This mechanistic approach to microbiota research will provide causal links between pathogen-mediated environmental remodeling and changes in microbial growth conditions that cannot be gleaned from solely cataloging bacterial species. Successful completion of this work will reveal opportunities to enhance innate host defenses by identifying and targeting the metabolic pathways enteric pathogens use to overcome colonization resistance.

项目概要微生物群是重要的前线屏障，可保护宿主免受微生物入侵并保持检查弗兰克病原体，如鼠伤寒沙门氏菌（STm），然而，它们善于克服微生物介导的定植抗性，从而导致生态失调和疾病。在体内平衡下，微生物群产生的抗菌短链脂肪酸 (SCFA) 可以保护宿主在感染过程中，STm 使用其 III 型分泌物来限制病原体复制。系统（T3SS）触发炎症反应，消耗 SCFA 产生的共生体。该范式认为，产生 SCFA 的物种的耗尽是管腔 STm 扩张的先决条件。然而，使用未使用抗生素的小鼠模型，我们观察到 STm 在 3-4 天前繁殖了 1000 倍当 SCFA 丰富时，明显炎症的发生以及微生物群落的组成这意味着 STm 采用了一种尚未描述的策略来恢复 pH 稳态并我们的初步研究结果表明，质子在胃肠道定植期间在 SCFA 存在的情况下生长。消耗代谢途径，包括氨基酸脱羧酶 CadA 和 SpeF，减轻 SCFA 体外生长抑制，并且是体内完全毒力所必需的，但尚不清楚这些途径是否在宿主体内存在 SCFA 的情况下特异性介导生长，或者 STm 如何确保代谢物在营养受限的胃肠道环境中为这些途径提供燃料。在胃肠道中，STm 使用其 T3SS 获取宿主衍生的氨基酸，为质子消耗提供能量在共生产生的 SCFA 存在下，反应并恢复 pH 稳态。本申请的目的是阐明 STm 如何适应肠道环境并使用基于这种理解，我开发了自己的独立研究计划，调查肠道病原体如何克服内在的保护障碍，以便我们可以发现新的治疗方法来增强在 AIM1 中，我们将评估质子消耗的贡献。体外 SCFA 存在下恢复 pH 稳态和生长的代谢途径，并进行研究这些途径在使用常规和限生素介导体内早期生态系统入侵中发挥的作用在 AIM2 中，我们将使用细菌遗传学、小鼠感染模型和代谢组学来确定。 STm 如何利用其毒力因子来设计支持菌群失调的新胃肠道生态位肠杆菌科在稳态条件下的扩张。这种微生物群研究的机械方法。将提供病原体介导的环境重塑与微生物生长变化之间的因果关系仅通过对细菌物种进行编目无法收集到的条件成功完成了这项工作。将揭示通过识别和靶向代谢途径来增强宿主先天防御的机会肠道病原体用于克服定植抗性。