The Ocean Nitrogen Imbalance Paradox: Environmental Controls on the Denitrification Isotope Effect

智力优势：本研究将测试反硝化同位素效应幅度对与海洋环境相关的培养条件的敏感性。在反硝化菌分批培养和连续培养实验中，探讨了同位素对电子供体、微量氧和温度的影响幅度。拟议的工作还将包括反硝化菌呼吸硝酸还原酶的酶同位素效应的测量，培养物中其酶活性的测量，以及反硝化菌株细胞硝酸盐运输动力学的检查。实验旨在揭示同位素效应振幅调制的生理基础，从而进一步解决这种在环境中的表现。更广泛的影响：考虑到本研究的广泛意义和重要性，这些新的实验数据将为在海洋模型中整合氮同位素动力学提供基础，以测试关键环境参数如何影响全球海洋氮同位素分布。此外，该提案将为研究生提供支持，该研究生将被介绍到广泛的技术和子学科，从微生物学和酶学到海洋学和稳定同位素生物地球化学。该项目涉及一名早期职业女性PI，她将在整个项目中指导一名研究生。

Intellectual Merit: This study will test the sensitivity of the amplitude of the denitrification isotope effect to culture conditions pertinent to the ocean environment. The isotope effect amplitude will be explored with respect to electron donor, trace oxygenation, and temperature, in both batch and continuous culture experiments of denitrifiers. The proposed work will also involve measurements of the enzymatic isotope effect of the respiratory nitrate reductase of denitrifiers, measurements of its enzymatic activity among cultures, and examination of cellular nitrate transport kinetics of denitrifying strains. The experiments are designed to reveal the physiological basis of the modulation of the isotope effect amplitude, which will further resolve this manifestation in the environment. Broader Impacts: In regards to the broader significance and importance of this study, these new experimental data will provide a basis for integration of nitrogen isotope dynamics in ocean models to test how key environmental parameters can affect the global ocean distribution of nitrogen isotopes. Moreover, the proposal will provide support for a graduate student, who will be introduced to a broad range of techniques and sub-disciplines, from microbiology and enzymology, to oceanography and stable isotope biogeochemistry. The project involves an early career female PI, who will mentor one graduate student throughout the project.