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.

项目总结/摘要 世界卫生组织将腹泻归类为一种重大的全球性健康威胁， 儿童日常摄入少量的传染性有机体可导致数万亿的病原体脱落 在凳子上。因此，我们推测肠道病原体，如肠出血性大肠杆菌。大肠杆菌具有强大的 获得营养物质的机制，提供在肠道中快速复制所需的能量。而 许多支持模式生物肠道定植的营养素是已知的， 对这些营养素的潜在竞争知之甚少。有了NIH的资助和研究策略 建立在链霉素处理的小鼠模型上，我们先前确定了支持定植的营养素 通过6株基因组测序、遗传学上易处理的、典型的致病性和耐药性E.大肠杆菌菌株。而 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亚群， 肠道中的可用营养物质。事实上，不同的E.大肠杆菌菌株可以彼此共定殖， 表明它们占据着不同的生态位。两个Escherosal E.大肠杆菌菌株被发现发挥定植 对E. coli O157：H7。另一方面，另外两种病理类型能够克服 殖民抵抗与相同的殖民者共同殖民。根据基本的生态学原理， 由竞争细菌占据的生态位由养分可利用性限定。一个重要的预测， 营养生态位假说认为，植物对入侵的抵抗力或敏感性取决于植物对营养物质的消耗， 当地的微生物群，但几乎没有支持证据。重要的是，我们最近证明了殖民化 抗性由兼性厌氧菌赋予。问题是：病原体如何克服殖民化 抵抗感染的能力吗在链霉素处理的竞争性定殖小鼠模型中， 可以操纵兼性微生物群，使其由精心选择的、充分表征的大肠杆菌组成。杆菌 对所选致病型发挥定殖抗性或不发挥定殖抗性的菌株。拟议研究 战略测试的假设，肠道病原体的成功入侵取决于有效的机制， 竞争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可获得的营养物质 测序将确定在竞争性E.大肠杆菌病原体和 肠道内的唾液。目的二是研究E.杆菌 病原体和寄生虫通过直接测量体内的营养消耗。为了鉴定等位基因 在赋予适应性优势的分解代谢基因的差异中，分解代谢操纵子将在 将在动物中评估菌株及其竞争适应性。这些实验旨在阐明 营养获取的机制是建立感染的关键。更好地了解如何 肠道病原体与微生物群竞争营养物是预防肠道感染所必需的。