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适应环境条件变化（如盐度增加）的相容溶质，因为它们不干扰细胞代谢。在海洋环境中，由于环境条件的改变，例如病毒攻击或放牧，这些化合物经常被释放到海水中。释放出的含氮渗透压物质是海洋微生物的重要营养物质，海洋微生物可以利用它们作为碳源、氮源和能源。众所周知，这些含氮渗透剂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，有助于反射阳光并导致气候变冷。迫切需要了解这些化合物的微生物代谢及其在海洋水体中的季节性循环，为了更好地了解它们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，基于最近发现的海洋生物中TMAO降解的新途径和开发强大的液相色谱-质谱联用技术的进展，尽管已经从申请人的实验室获得了用于同时定量这些含氮渗透物的LC-ESI-MS方法，但该及时的提议旨在确定表层海水中含氮渗透物的季节性循环，并解决这些环境相关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在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方面的知识空白。利用新开发的分析技术，我们的目标是确定的季节性周期的表层海水中的含氮渗透剂和微生物的氧化活动的常设浓度。这些数据将被纳入一个地球化学模式，为未来的预测气候变化下的N-渗透物的地球化学循环。本研究以培养的模式生物为研究对象，通过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含氮渗透剂代谢的关键微生物。这项工作将为我们了解这些渗透剂的微生物转化提供新的知识。含氮化合物，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作为一个领先的国家，不仅在海洋生物化学循环和海洋微生物学的研究，而且在环境科学的尖端技术的发展。

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 solute in response to changes in environmental conditions, such as increasing salinity, because they do not interfere with cell metabolisms. They also have beneficial effects in protecting proteins against denaturation due to chemical or physical damages.In the marine environments, these compounds are frequently released into the sea water due to the change of environmental conditions, such as viral attack 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 of 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 on the discovery of the 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 the 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 marine carbon and nitrogen cycles and the contribution of these compounds in future climate change through the release of climate-active molecules. Using 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 to 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 microbial transformation of these nitrogen containing compounds, and will fill in 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 the research of marine biogeochemical cycles and marine microbiology, but also in the development of cutting edge technology in environmental science.