Biogeochemical cycling of N-osmolytes in the surface ocean

含氮化合物，包括甘氨酸甜菜碱（GBT）、胆碱和三甲胺n-氧化物（TMAO）在海洋生物中普遍存在。它们被海洋生物用作相容溶质，以应对环境条件的变化，例如盐度的增加，因为它们不干扰细胞代谢。它们在保护蛋白质不因化学或物理损伤而变性方面也有有益的作用。在海洋环境中，由于环境条件的变化，例如病毒裂解或放牧，这些化合物经常从这些生物中直接释放到海水中。释放的含氮渗透物是海洋微生物的重要营养物质，可以作为碳、氮和能量的来源。众所周知，这些含氮渗透物的降解有助于释放气候活性气体，包括挥发性甲基化胺。甲基化胺是海洋大气中气溶胶的重要来源，它有助于反射阳光并对气候产生冷却效应。为了更好地了解这些化合物在海洋生物地球化学循环中的作用，以及它们在未来气候变化中的作用，迫切需要了解这些化合物在海洋水体中的微生物代谢及其季节循环。基于最近在海洋生物中TMAO降解新途径的发现和高效液相色谱-质谱（LC-ESI-MS）同时定量这些含氮渗透物的发展进展，这项及时的提案旨在确定表层海水中含氮渗透物的季节性循环，并解决这些与环境相关的化合物如何降解以及参与该过程的主要微生物是什么。所产生的数据将填补我们对海洋碳和氮循环以及这些化合物通过释放气候活性分子对未来气候变化的贡献的知识的主要空白。利用新开发的分析技术，我们旨在确定表层海水中氮渗透物浓度和微生物氧化活性的季节周期。这些数据将被纳入生物地球化学模型，用于未来气候变化下氮渗透物生物地球化学循环的预测。利用培养的模式生物，我们旨在确定海洋浮游微生物降解GBT和TMAO的关键基因、酶和代谢途径。利用分子和单细胞操作技术，我们的目标是进一步确定参与英吉利海峡表层海水中氮渗透物代谢的关键微生物。这项工作将为我们对这些含氮化合物的微生物转化的理解提供新的知识，并将填补海洋碳和氮循环知识的严重空白。该项目预计将进一步加强英国在海洋生物地球化学循环和海洋微生物学研究以及环境科学前沿技术发展方面的领先地位。

Nitrogen-containing compounds, including glycine betaine (GBT), choline and trimethylamine N-oxide (TMAO) are ubiquitous in marine organisms. They are used by marine organisms as compatible solutes in response to changes in environmental conditions, such as increasing salinity, because they do not interfere with cell metabolism. They also have beneficial effects in protecting proteins against denaturation due to chemical or physical damage.In the marine environment, these compounds are frequently released from these organisms directly into seawater due to changing environmental conditions, such as by viral lysis or grazing. The released nitrogenous osmolytes serve as important nutrients for marine microorganisms, which can use them as carbon, nitrogen and energy sources. It is well known that the degradation of these nitrogenous osmolytes contribute to the release of climate-active gases, including volatile methylated amines. Methylated amines are important sources of aerosols in the marine atmosphere, which help to reflect sunlight and cause a cooling effect on the climate. There is an urgent need to understand the microbial metabolism of these compounds and their seasonal cycles in the marine water column, in order to better understand their role in marine biogeochemical cycles and their role in future climate change.Built on the recent progress of the discovery of a new pathway of TMAO degradation in marine organisms and the development of a powerful liquid chromatography with mass spectrometry (LC-ESI-MS) method for simultaneous quantification of these nitrogenous osmolytes from the applicants' laboratories, this timely proposal aims to determine the seasonal cycle of nitrogenous osmolytes in surface seawater and to address how these environmentally-relevant compounds are degraded and what are the major microorganisms that are involved in the process. The data generated will fill in a major gap in our knowledge of the marine carbon and nitrogen cycles and the contribution of these compounds in future climate change through the release of climate-active molecules. Using the newly developed analytic techniques, we aim to determine the seasonal cycle of standing concentrations of nitrogenous osmolytes in the surface seawater and microbial oxidation activities. These data will be incorporated into a biogeochemical model for future prediction of biogeochemical cycles of N-osmolytes under climate change. Using cultivated model organisms, we aim to define the key genes, enzymes and the metabolic pathways in GBT and TMAO degradation by marine planktonic microbes.Using molecular and single cell manipulation techniques, we aim to further determine the key microbial players involved in the metabolism of nitrogenous osmolytes in surface seawater from the English Channel.This work will generate novel knowledge about our understanding of the microbial transformation of these nitrogen containing compounds, and will fill a serious gap in knowledge of marine carbon and nitrogen cycles. The project is expected to further strengthen the UK as a leading country not only in research of marine biogeochemical cycles and marine microbiology, but also in the development of cutting edge technology in environmental science.