Is bacterial DMS consumption dependent on methylamines in marine waters?

二甲硫化物（DMS）是构成“海洋气味”的气体混合物中的关键成分。海洋表面的单细胞生物每年产生大约3亿吨DMS。这些DMS中有一小部分（高达16%）被释放到大气中，形成能影响我们天气和气候的降雨化合物。下雨时，含硫化合物会沉积回大陆的土壤中。然而，大多数在海洋中形成的DMS留在那里，面对海洋微生物的消耗和转化为另一种含硫化合物-二甲基亚砜（DMSO）。DMSO通常是海洋中最丰富的有机硫化合物，代表了基本生命元素硫和碳的主要库。海水中含有丰富的重要化学营养物质，支撑着整个海洋食物网。溶解的有机氮池是一种化学“驱动通道”，其中含有高活性的n -渗透物：甘氨酸甜菜碱、胆碱和三甲胺n -氧化物。这些化学物质被微生物用来保护它们免受环境条件变化的影响，比如周围海水盐度的变化，并保护它们的细胞免受化学或物理损伤。当n -渗透物分解时，它们会将甲胺等气体释放到大气中，从而影响气候。我们在细菌分解有机氮化合物（如甲胺）和有机硫化合物（如DMS）之间发现了一种以前未被认识到的有趣联系。这种联系是由一种叫做三甲胺单加氧酶（TMM）的细菌酶提供的。TMM同时去除海水中的甲胺和DMS（将其转化为DMSO）。事实上，如果没有甲胺的存在，二甲基亚砜的产生是不会发生的。我们估计，海洋中多达20%的细菌含有这种特殊的酶。我们想要开展的研究将首先调查实验室中“模型”微生物中DMS去除和甲胺可用性之间的联系，检查这种联系是否活跃，以及如何在全球海洋中常见的关键海洋细菌中控制这种联系。接下来，我们将确定这一过程与其他消耗海水中DMS的生物过程相比的重要性，并为使用这种酶去除DMS的微生物命名。作为普利茅斯海洋实验室协调的西海峡天文台的一部分，我们将在每周一次采样的一个站点研究连接英吉利海峡有机硫和氮循环的微生物过程。这是一个长期存在的时间序列站点，可以获得丰富的海洋学和生物学数据（藻类多样性，温度，营养物质等；http://www.westernchannelobservatory.org.uk），我们将能够使用这些数据。一个全球大气颗粒模型最近表明，通过气候驱动的浮游植物物种分布的变化，DMS排放地点的变化可能对我们的气候产生强烈影响。因此，我们想要调查DMS去除、有机氮化合物如甲胺的可用性和浮游植物物种之间的联系，我们可以在L4站做，在那里浮游植物物种演替被理解，可以很容易地取样。我们将把这个温带沿海地区与地球上DMS热点之一——南大洋进行比较。与北半球严重污染的空气相比，这片遥远而孤立的海洋上方的大气是原始的。在这里，海洋中产生的DMS与我们的气候之间的联系被认为是最强的。鉴于DMS的重要作用，确定海洋微生物的作用和DMS从海水中去除的途径将提供关键信息，这将提高我们未来对硫循环如何影响我们气候的理解。

Dimethylsulfide (DMS) is a key ingredient in the cocktail of gases that makes up the 'smell of the sea'. Around 300 million tons of DMS are formed each year by single-celled organisms in the surface ocean. A small proportion (up to 16%) of this DMS is released into the atmosphere, forming cloud-seeding compounds which can influence our weather and climate. When it rains, sulfur compounds are deposited back into the soils of our continents. However, most of the DMS formed in the oceans stays there, facing consumption by marine microbes and conversion to another sulfur compound - dimethylsulfoxide (DMSO). DMSO is usually the most abundant organic sulfur compound in the oceans and represents a major pool of the essential life elements sulfur and carbon.Seawater contains a rich mixture of important chemical nutrients that support the entire oceanic food web. The dissolved organic nitrogen pool is a chemical 'drive thru' which contains the highly reactive N-osmolytes: glycine betaine, choline and trimethylamine N-oxide. These chemicals are used by microorganisms to protect them from changes in their environmental conditions, such as variability in the saltiness of the surrounding seawater, and to protect their cells from chemical or physical damage. When N-osmolytes breakdown they can release gases such as methylamines into the atmosphere which can influence the climate.We have found a previously unrecognised and intriguing link between the bacterial breakdown of organic nitrogen compounds, like methylamines, and organic sulfur compounds like DMS. This link is provided by a bacterial enzyme called trimethylamine monooxygenase (TMM). TMM simultaneously removes both methylamines and DMS from seawater (converting it to DMSO). In fact this production of DMSO doesn't happen without the presence of methylamines. We estimate that up to 20% of all bacteria in our oceans contain this particular enzyme. The research we want to carry out will firstly investigate this link between DMS removal and methylamine availability in 'model' micro-organisms in the laboratory, checking that this link is active and how it is controlled in key marine bacteria commonly found in the global oceans. We will next determine the importance of this process compared to other biological processes that consume DMS in seawater and put names to the microbes using this enzyme to remove DMS. We will study the microbial processes linking the organic sulfur and nitrogen cycles in the English Channel at a station that is sampled weekly as part of the Western Channel Observatory which is coordinated by Plymouth Marine Laboratory. This is a long-standing time series site for which a wealth of oceanographic and biological data are available (algal diversity, temperature, nutrients etc.; http://www.westernchannelobservatory.org.uk), which we will be able to use. A global model of particles in the atmosphere has recently suggested that changes in the location of DMS emissions, through climate-driven changes in the phytoplankton species distributions, could strongly influence our climate. We therefore want to investigate the link between DMS removal, the availability of organic nitrogen compounds like methylamines and phytoplankton species, which we can do at station L4, where phytoplankton species succession is understood and can be easily sampled.We will compare this temperate coastal region to one of the Earth's DMS hotspots - the Southern Ocean. The atmosphere above this remote and isolated ocean is pristine in comparison to the heavily polluted air of the Northern Hemisphere. Here, the connection between DMS produced in the oceans and our climate is thought to be the strongest. Given the important role of DMS, identifying the role of marine microorganisms and the pathways of DMS removal from seawater will provide key information that will improve our future understanding of how the sulfur cycle influences our climate.