Collaborative Research: Do Diverse Members of the Epsilonproteobacteria Employ a Novel Nitrate Reduction Pathway?

智力价值：氮是所有生物生长所需的一种关键营养物质。氮主要以气体形式存在于地球上，绝大多数生物无法同化。因此，固定氮，无论是铵、亚硝酸盐还是硝酸盐，都被激烈地争夺。地球表面氮素的大部分转化是由微生物催化的，包括不同固定氮素物种之间的相互转化。生长的首选氮素是铵，这通常是生态系统中的一种限制性营养物质。这个项目将详细介绍一种新的方法，通过这种方法，某些微生物可以“呼吸”或呼吸硝酸盐并产生铵。它们这样做的原因与人类呼吸氧气的原因相同，以节省能量。硝酸盐呼吸本身并不新鲜，但本研究的主要模式细菌深水鹦鹉螺使用的机制是新的，可能对它在深海热液喷口谋生很重要。还将研究携带编码相同途径的基因的深水假单胞菌的亲属，这些基因最常与动物有关，例如在人类的口腔和鸡的肠道中。这一途径对这些生物的益处目前尚不清楚。通过了解这些细菌的氮代谢，我们将更多地了解氮在环境中的移动，也许还会了解动物相关细菌如何在远离宿主的环境中生存。该项目旨在利用基因组科学中最新的技术进步，即高通量转录组学，并将其与更传统的生理学方法相结合，以表征这一新的硝酸盐还原途径。该项目最终将确定这一途径的关键酶和中间体，以及它是如何受到调控的。更广泛的影响：PIS将培训几名本科生和两名研究生基因组使能微生物生理学，通过跨机构和跨学科的研究加强学习。除了传统的微生物生理学和基础氮化学之外，所有学生都将接触到最先进的高通量基因组学方法。他们将通过讲习班接受负责任的研究方面的正式培训，并将通过在国家会议和出版物上作陈述，以口头和书面形式介绍他们的研究，从而加强他们的专业发展。这些活动将被纳入国家科学基金会资助的硝化网络RCN的战略计划。最后，这些成果将通过教师培训讲习班向K-12学生传播，并通过特拉华大学的海岸日等活动向公众传播，年平均出席人数超过8,000人，以及其他活动，因为有机会由私人投资机构进行不那么正式的演讲。

Intellectual Merit:Nitrogen is a key nutrient that all living beings need to grow. Nitrogen exists on planet Earth predominantly in gaseous form, inaccessible for assimilation to the vast majority of organisms. Hence fixed nitrogen, either as ammonium, nitrite or nitrate, is competed for vigorously. Most transformations of nitrogen in the Earth's surface are catalyzed by microbes including the interconversion between different fixed nitrogen species. The preferred nitrogen species for growth is ammonium, often a limiting nutrient in ecosystems. This project will detail a new means by which certain microbes "breathe" or respire nitrate and produce ammonium. They do this for the same reason humans breathe oxygen, to conserve energy. Nitrate respiration is not new per se, but the mechanism used by the primary model bacterium for this study, Nautilia profundicola, is novel and may be important for it to making a living at deep-sea hydrothermal vents. Relatives of N. profundicola will also be studied that carry the genes encoding the same pathway and are most often found in association with animals, for example in the oral cavity of humans and in the guts of chickens. The benefit of this pathway to these organisms is currently unclear. By understanding the nitrogen metabolism of these bacteria, we will learn more about how nitrogen moves in the environment and perhaps also how animal-associated bacteria survive in the environment away from their hosts. This project is designed to take advantage of the most recent technological advances in genome sciences, namely high-throughput transcriptomics, and combine it with more traditional physiological approaches to characterize this novel nitrate reduction pathway. This project will ultimately define the key enzymes and intermediates of this pathway and how it is regulated. Broader Impacts:The PIs will train several undergraduate students and two graduate students in genome-enabled microbial physiology, enhancing learning through cross-institutional and cross-disciplinary research. All students will be exposed to state of the art high-throughput genomics approaches in addition to traditional microbial physiology and basic nitrogen chemistry. They will be formally trained in the responsible conduct of research through workshops and their professional development will be enhanced by presenting their research in both oral and written form via presentations at national meetings and publications. These activities will be integrated into the strategic plan of the NSF-funded Nitrification Network RCN. Finally, these results will be disseminated to K-12 students via teacher-training workshops and to the public via events like the University of Delaware's Coast Day, with an average annual attendance of over 8,000, and others as opportunities arise for less formal presentations by the PIs.