Collaborative Research: Direct Oxidation of Organic Nitrogen by Marine Ammonia Oxidizing Organisms

合作研究：海洋氨氧化生物直接氧化有机氮

• 批准号: 1538677
• 负责人: James Hollibaugh
• 金额: $ 48.08万
• 依托单位: University of Georgia Research Foundation Inc
• 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: 2015-12-01 至 2018-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1538677&HistoricalAwards=false
• 关键词: Collaborative; Research; Direct; Oxidation; Organic

Nitrogen is an essential nutrient for phytoplankton that often limits primary production in the ocean, and its availability therefore plays a key role in global ocean productivity. The amounts and form in which nitrogen exist are controlled by microorganisms. One microorganism-mediated process is known as nitrification, which oxidizes ammonia or ammonium to nitrite and nitrite to nitrate, nitrate being the bioavailable form of nitrogen. While this is the well-accepted process of nitrification, preliminary results strongly suggest that a nitrogen-containing compound know as polyamine nitrogen may be directly converted by some microorganisms to nitrate. However, the importance of this process for global biogeochemical nitrogen cycling is unknown. The goal of this study is to evaluate the biogeochemical significance of direct oxidation of polyamine nitrogen, as a model organic nitrogen compound, to nitrification compared to canonical nitrification of ammonia. The project will result in training a postdoctoral researcher and provide opportunities for undergraduates to gain hands-on experience with research on microbial geochemistry and coastal ecosystem processes. Project personnel will also work with the Georgia Coastal Ecosystems Long-Term Ecological Research program to engage a K-12 science teacher in the project.Ammonia oxidation is a key step in the process of converting fixed nitrogen to dinitrogen gas and thus is central to the global nitrogen cycle and to removing excess fixed nitrogen from coastal waters with high concentrations of nutrients. Recent research has shown that Thaumarchaeota play a major role in ammonia oxidation in the ocean. Experiments with enrichment cultures and coastal water samples where ammonia oxidizing archaea are the dominant ammonia oxidizers, show that some forms of organic nitrogen may be oxidized directly to nitrogen oxides without first being regenerated as ammonium. Of the substrates tested, polyamine and particularly putrescine nitrogen appear to be oxidized directly to nitrogen oxides, while amino acid and urea nitrogen is first regenerated as ammonium and then oxidized. The investigators will examine this process in detail over three years using enrichment cultures and experiments conducted with coastal bacterioplankton. Specifically, they will aim to better understand 1) the consequences of this novel process to ocean geochemistry, 2) the fate of the carbon present in polyamines, 3) what organisms are responsible for the direct oxidation, and 4) the chemical characteristics of the organic nitrogen compounds accessible to direct oxidation.

氮是浮游植物的必不可少的营养素，通常会限制海洋中的主要产量，因此其可用性在全球海洋生产力中起着关键作用。存在氮的数量和形式由微生物控制。一种微生物介导的过程被称为硝化作用，将氨或铵氧化为亚硝酸盐和亚硝酸盐，硝酸盐氧化为硝酸盐，硝酸盐是氮的生物利用形式。虽然这是硝化的良好接受过程，但初步结果强烈表明，含氮的化合物被称为多胺氮可以直接被某些微生物转化为硝酸盐。但是，该过程对全球生物地球化学氮循环的重要性尚不清楚。这项研究的目的是评估多胺氮直接氧化作为模型有机氮化合物的生物地球化学意义，与氨的硝化相比。该项目将导致培训博士后研究人员，并为大学生提供有关微生物地球化学和沿海生态系统过程研究的动手经验的机会。项目人员还将与佐治亚州沿海生态系统的长期生态研究计划合作，与K-12科学老师一起参与该项目。Mammonia氧化是将固定氮转化为Dinitrogen气体的关键步骤，因此对于全球氮气周期和从高度浓度的固定氮气中移除了过多的固定氮气。最近的研究表明，Thaumarchaeota在海洋中的氨氧化中起着重要作用。富集培养物和沿海水样的实验是氧化古细菌是主要的氨氧化剂，表明某些形式的有机氮可以直接氧化为氮氧化物，而不会先再生为ammhonium。在测试的底物中，多胺，特别是腐烂的氮似乎直接被氧化为氮氧化物，而氨基酸和尿素氮首先被以铵的含量再生，然后再氧化。研究人员将使用沿海细菌的富集培养和实验进行详细研究这一过程。具体而言，他们将旨在更好地理解1）新型过程对海洋地球化学的后果，2）多胺中存在的碳的命运，3）哪些生物造成了直接氧化的原因； 4）有机氮化合物可用于直接氧化的有机氮化合物的化学特性。