Mechanism of Salmonella-dependent disruption of propionate-mediated colonization resistance

沙门氏菌依赖性破坏丙酸介导的定植抗性的机制

• 批准号: 10388829
• 负责人: CATHERINE SHELTON
• 金额: $ 3.2万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10388829
• 关键词: Anaerobic Bacteria; Bacteroides; Bacteroides thetaiotaomicron; Carbon; Catabolism; Cessation of life; Complex; Data; Epithelial Cells; Exposure to; Fermentation; Fluorescence Microscopy; Gastroenteritis; Gastrointestinal tract structure; Genes; Germ-Free; Growth; In Vitro; Infection; Inflammation; Inflammatory Response; Intestines; Invaded; Literature; Measures; Mediating; Metabolism; Modeling; Mus; Nitrates; Nutrient; Operon; Oxidants; Oxygen; Pilot Projects; Production; Propionates; Pyruvate; Research; Respiration; Role; Salmonella; Salmonella enterica; Salmonella typhimurium; Series; Signal Transduction; Source; Testing; Toxic effect; Training; Volatile Fatty Acids; Work; bacterial community; colonization resistance; commensal bacteria; diarrheal disease; enteric pathogen; experimental study; gut colonization; gut inflammation; gut microbiota; in vivo; innovation; insight; member; microbiota; mouse model; mutant; non-typhoidal Salmonella; novel; pathogen; pathogenic bacteria; resident commensals

PROJECT SUMMARY Infection with non-typhoidal Salmonella is a significant cause of diarrheal disease worldwide, causing approximately 150 million illnesses and 60,000 deaths each year. In the gastrointestinal tract, S. Tm encounters the resident commensal bacteria (gut microbiota). The gut microbiota protects the host against invading pathogens (colonization resistance) and limits pathogen expansion. Propionate, a short-chain fatty acid produced by members of the gut microbiota, is predicted to mediate colonization resistance against S. Tm by down-regulating invasion and inhibiting growth. As a successful pathogen, S. Tm may possess mechanisms to mitigate the toxic effects of propionate. Discovery of the prpBCDE operon, which enables S. Tm to metabolize propionate into pyruvate, provided initial insight into the ability of S. Tm to overcome propionate inhibition. However, it remains unknown under what conditions S. Tm uses the prpBCDE operon to eliminate intracellular propionate. During infection, the host's inflammatory response provides electron acceptors that allow S. Tm to metabolize diverse nutrients into carbon sources to support pathogen growth. My data suggests that propionate serves as a carbon source for S. Tm, specifically during anaerobic respiration when inflammation-derived electron acceptors are present. In preliminary experiments, I determined that inflammation-derived electron acceptors also alter propionate-dependent changes in expression of S. Tm invasion machinery. Thus, inflammation-derived electron acceptors may provide S. Tm with the opportunity to eliminate the inhibitory effects of propionate and fuel growth during infection. Indeed, my pilot studies demonstrate that propionate metabolism benefits S. Tm in vivo as a wildtype strain of S. Tm had a growth advantage over a prpC mutant strain in mouse models of S. Tm gastroenteritis. Therefore, the central hypothesis of this proposal is that S. Tm metabolizes propionate in the inflamed gut to regulate its invasion and support its luminal growth, ultimately allowing this pathogen to overcome propionate-dependent colonization resistance. To test this hypothesis, I will use an innovative combination of commensal members of the gut microbiota and S. Tm mutant strains along with germ- free and conventional mouse models to explore how S. Tm contends with propionate during infection. Experiments proposed in Aim 1 will determine if propionate serves as a carbon source to fuel S. Tm growth in vitro and in vivo. In Aim 2, I will identify if gut inflammation and anaerobic respiration are required for propionate metabolism to be beneficial to S. Tm during infection. Aim 3 will investigate if propionate metabolism not only fuels growth by providing a carbon source during respiration but by signaling to S. Tm to decrease invasion. If successful, this research will challenge the dogma that short-chain fatty acids inhibit Salmonella growth in the gut. This project will describe how S. Tm mitigates the detrimental effects of propionate by metabolizing this metabolite into a usable carbon source to fuel growth. 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世界腹泻病的一个重要原因，导致 每年约有 1.5 亿人患病，6 万人死亡。在胃肠道中，S.Tm遇到 常驻共生细菌（肠道微生物群）。肠道微生物群保护宿主免受入侵 病原体（定植抗性）并限制病原体扩张。丙酸，一种短链脂肪酸 由肠道微生物群成员产生，预计可通过以下方式介导针对 S. Tm 的定植抗性： 下调侵袭并抑制生长。作为一种成功的病原体，S.Tm 可能具有以下机制： 减轻丙酸盐的毒性作用。发现 prpBCDE 操纵子，使 S.Tm 能够代谢 丙酸转化为丙酮酸，初步了解了 S.Tm 克服丙酸抑制的能力。 然而，目前尚不清楚S.Tm在什么条件下使用prpBCDE操纵子来消除细胞内的 丙酸盐。在感染期间，宿主的炎症反应提供电子受体，使 S.Tm 将多种营养物质代谢为碳源以支持病原体生长。我的数据表明丙酸盐 作为 S.Tm 的碳源，特别是在炎症引起的无氧呼吸期间 存在电子受体。在初步实验中，我确定炎症衍生的电子 受体还改变S.Tm入侵机制表达中丙酸依赖性变化。因此， 炎症衍生的电子受体可能为S.Tm提供消除抑制作用的机会 感染期间丙酸盐和燃料生长。事实上，我的初步研究表明丙酸代谢 作为 S.Tm 野生型菌株在体内的益处 S.Tm 在小鼠体内比 prpC 突变菌株具有生长优势 S.Tm胃肠炎模型。因此，该提案的中心假设是S.Tm代谢 丙酸在发炎的肠道中调节其入侵并支持其管腔生长，最终允许这种情况 病原体克服丙酸盐依赖性定植抗性。为了检验这个假设，我将使用 肠道微生物群的共生成员和 S.Tm 突变菌株以及细菌的创新组合 自由和传统小鼠模型来探索 S.Tm 在感染过程中如何与丙酸盐抗衡。 目标 1 中提出的实验将确定丙酸盐是否作为碳源来促进 S.Tm 的生长 体外和体内。在目标 2 中，我将确定丙酸盐是否需要肠道炎症和无氧呼吸 感染期间的代谢有利于S.Tm。目标 3 将研究丙酸代谢是否不仅 通过在呼吸过程中提供碳源来促进生长，同时通过向 S.Tm 发出信号来减少入侵。如果 如果成功，这项研究将挑战短链脂肪酸抑制沙门氏菌生长的教条 肠道。该项目将描述 S.Tm 如何通过代谢丙酸盐来减轻丙酸盐的有害影响 代谢成可用碳源以促进生长。预期的发现将提供更深入的了解 这种细菌病原体利用一种新机制来逃避肠道微生物群并建立感染。