Mechanisms of Nutrient Competition in the Intestine

肠道营养竞争机制

• 批准号: 9220348
• 负责人: TYRRELL CONWAY
• 金额: $ 30.4万
• 依托单位: OKLAHOMA STATE UNIVERSITY STILLWATER
• 依托单位国家: 美国
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-01 至 2021-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9220348
• 关键词: Alleles; Anaerobic Bacteria; Animal Model; Animals; Bacteria; Child; Communities; Consumption; Diarrhea; Disease; Ecosystem; Enteral; Enterobacteriaceae; Environment; Escherichia coli; Escherichia coli EHEC; Escherichia coli O157:H7; Feces; Funding; Genes; Genome; Genomics; Growth; Health; Human; In Vitro; Infection; Infection prevention; Infectious Agent; Ingestion; Intestines; Invaded; Kinetics; Laboratory culture; Large Intestine; Lead; Maintenance; Measurement; Measures; Microbe; Modeling; Mucous body substance; Mus; Nutrient; Nutritional; Operon; Pathogenesis; Pathogenicity; Pathway interactions; Physiology; Population; Process; Property; RNA; Research; Resistance; Resources; Sampling; Source; Streptomycin; Symbiosis; System; Testing; United States National Institutes of Health; World Health Organization; base; commensal microbes; design; enteric pathogen; experimental study; feeding; fitness; gut microbiota; in vivo; insight; killings; metabolomics; microbiota; microorganism; mouse model; mutant; pathogen; pathogen genome; prevent; success; transcriptome sequencing; transcriptomics

PROJECT SUMMARY/ABSTRACT The World Health Organization classifies diarrhea as a significant worldwide health threat, killing thousands of children daily. Ingestion of a small number of infectious organisms can lead to trillions of pathogens being shed in the stool. Therefore, we postulate that enteric pathogens such as enterohemorrhagic E. coli possess potent mechanisms for obtaining nutrients that provide the energy needed to replicate rapidly in the intestine. While many of the nutrients that support intestinal colonization by model organisms are known, the mechanisms underlying competition for those nutrients are poorly understood. With NIH funding and a research strategy built on the streptomycin treated mouse model, we previously identified the nutrients that support colonization by six genome-sequenced, genetically tractable, prototypical pathogenic and commensal E. coli strains. While these bacteria essentially use the same growth substrates in laboratory culture, each uses a different subset of the available nutrients in the intestine. Indeed, different E. coli strains can co-colonize with one another, indicating that they occupy distinct niches. Two commensal E. coli strains were found to exert colonization resistance against E. coli O157:H7. On the other hand, two other pathotypes were able to overcome colonization resistance to co-colonize with the same commensals. According to basic ecological principles, the niches occupied by competing bacteria are defined by nutrient availability. An important prediction of the nutrient-niche hypothesis is that resistance or sensitivity to invasion depends on nutrient consumption by the resident microbiota, but there is little supporting evidence. Importantly, we recently proved that colonization resistance is imparted by the facultative anaerobes. The question is: how do pathogens overcome colonization resistance to initiate infections? In the streptomycin treated mouse model of competitive colonization, the facultative microbiota can be manipulated to consist of carefully chosen, well-characterized commensal E. coli strain(s) that either exert colonization resistance, or not, against selected pathotypes. The proposed research strategy tests the hypothesis that successful invasion by enteric pathogens depends on potent mechanisms to compete for the nutrients needed to replicate in the intestine. In Aim 1 the competitive colonization model will be used to measure the nutrients that are available to invading pathogens and genome-specific RNA sequencing will determine the catabolic gene systems that are induced in the competing E. coli pathogens and commensals in the intestine. Aim 2 will focus on the mechanisms of nutrient competition between E. coli pathogens and commensals by direct measurement of nutrient consumpition in vivo. To identify allelic differences in catabolic genes that confer fitness advantages, catabolic operons will be swapped between strains and their competitive fitness will be assessed in animals. These experiments are designed to elucidate the mechanisms of nutrient acquisition that are critical to establishing infection. A better understanding of how enteric pathogens compete with the microbiota for nutrients is needed to prevent intestinal infections.

项目概要/摘要 世界卫生组织将腹泻列为全球重大健康威胁，导致数千人死亡 孩子们每天。摄入少量传染性生物体可能导致数万亿病原体脱落 在凳子里。因此，我们假设肠出血性大肠杆菌等肠道病原体具有强效 获取营养物质的机制，这些营养物质提供在肠道中快速复制所需的能量。尽管 许多支持模型生物肠道定植的营养物质是已知的，其机制 人们对这些营养素的潜在竞争知之甚少。凭借 NIH 的资助和研究策略 基于链霉素治疗的小鼠模型，我们之前确定了支持定植的营养物质 由六种基因组测序的、遗传上易于处理的、典型的致病性和共生大肠杆菌菌株组成。尽管 这些细菌在实验室培养中基本上使用相同的生长基质，每种细菌使用不同的子集 肠道内可利用的营养物质。事实上，不同的大肠杆菌菌株可以彼此共定殖， 表明它们占据着独特的利基市场。发现两种共生大肠杆菌菌株能够进行定植 对大肠杆菌 O157:H7 的抗性。另一方面，另外两种致病型能够克服 与相同共生体共定殖的定殖抗性。根据基本生态原理， 竞争性细菌占据的生态位由营养可用性决定。一个重要的预测 营养生态位假说认为，对入侵的抵抗力或敏感性取决于生物体的营养消耗 常驻微生物群，但几乎没有支持证据。重要的是，我们最近证明了殖民 抵抗力是由兼性厌氧菌赋予的。问题是：病原体如何克服定植 抵抗引发感染？在链霉素治疗的竞争性定植小鼠模型中， 可以操纵兼性微生物群，使其由精心选择的、特征良好的共生大肠杆菌组成 对选定的致病型具有或不具有定植抗性的菌株。拟议的研究 该策略检验了这样的假设：肠道病原体的成功入侵取决于有效的机制 争夺在肠道内复制所需的营养。在目标 1 中，竞争性殖民模型将 用于测量入侵病原体和基因组特异性 RNA 可用的营养物质 测序将确定在竞争性大肠杆菌病原体中诱导的分解代谢基因系统， 肠道内的共生体。目标2将重点关注大肠杆菌之间的营养竞争机制 通过直接测量体内营养消耗来识别病原体和共生体。鉴定等位基因 分解代谢基因的差异赋予适应性优势，分解代谢操纵子将在 菌株及其竞争适应性将在动物身上进行评估。这些实验旨在阐明 对建立感染至关重要的营养获取机制。更好地理解如何 肠道病原体与微生物群竞争预防肠道感染所需的营养。