DISSERTATION RESEARCH: Quantifying Nitrogen Limitation in the Gut Microbiota

论文研究：量化肠道微生物群中的氮限制

• 批准号: 1501495
• 负责人: Lawrence David
• 金额: $ 1.97万
• 依托单位: Duke University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-15 至 2017-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1501495&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Quantifying; Nitrogen; Limitation

The availability of different types of nutrients can determine which species are able live together. When microbes (such as bacteria) live inside animals (such as humans), they may compete for a limited nutrient (such as nitrogen) or may cooperate with each other to acquire that same nutrient. This project will examine how humans and the bacteria in their guts manage their needs for nitrogen. Humans get nitrogen from their diet, and gut bacteria get nitrogen from inside their human hosts. The bacteria can either compete with humans for nitrogen in swallowed food or they can be "fed" through material that humans excrete into the gut. The researchers will focus on competition for nitrogen in the gut and test whether it is important in determining which species of bacteria can live there. The results of this work may help in the design of treatments that require a change in the community of bacteria living in the guts of sick people and domestic animals.The hypothesis that nitrogen is limiting in the gut comes from the observation that most indigestible material reaching the large intestine is nitrogen poor and, therefore, there is little nitrogen available to most of the gut's microbiota. This leads to two testable predictions. First, there is a longitudinal gradient in the environmental (non-microbial) carbon-to-nitrogen (C:N) ratio and a depletion of diet-sourced nitrogen along a healthy gut. Second, much of the nitrogen used by bacteria must come from host secretions. These predictions will be tested by measuring C:N ratios along the gut and by using stable isotope tracer studies to identify the fate of dietary nitrogen and the source of bacterial nitrogen. Finally, to determine if changes in nitrogen availability can alter microbial community composition in the gut, in vitro co-culture competition experiments will be conducted under varying levels of nitrogen availability.

不同类型的营养物质的可用性可以决定哪些物种能够共同生活。当微生物（如细菌）生活在动物（如人类）体内时，它们可能会竞争有限的营养素（如氮），或者可能会相互合作以获得相同的营养素。该项目将研究人类和肠道中的细菌如何管理他们对氮的需求。人类从饮食中获得氮，肠道细菌从人类宿主体内获得氮。这种细菌既可以与人类竞争吞咽食物中的氮，也可以通过人类排泄到肠道中的物质来“喂养”它们。研究人员将专注于肠道中氮的竞争，并测试它是否对确定哪些细菌物种可以在那里生活很重要。这项工作的结果可能有助于设计需要改变病人和家畜肠道中细菌群落的治疗方法。氮在肠道中是有限的假设来自于观察到大多数到达大肠的难消化物质是氮缺乏的，因此，大多数肠道微生物群几乎没有氮。这导致了两个可检验的预测。首先，在环境（非微生物）碳-氮（C：N）比中存在纵向梯度，并且沿着健康肠道沿着消耗饮食来源的氮。第二，细菌使用的大部分氮必须来自宿主的分泌物。这些预测将通过测量沿着肠道的C：N比和使用稳定同位素示踪研究来确定膳食氮的命运和细菌氮的来源来进行测试。最后，为了确定氮可用性的变化是否会改变肠道中的微生物群落组成，将在不同水平的氮可用性下进行体外共培养竞争实验。