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.
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.