Microbial degradation of dimethylsulfoxide in the marine environment

二甲基亚砜（DMSO）是一种用途广泛的化学品。它是一种广泛使用的溶剂，例如在制药应用中，以及造纸工业的废物。它也天然存在于一系列水果中，如乌藨子和蔬菜。然而，DMSO也是天然硫循环的一部分。硫是所有生命的基本元素，其有机形式是所有蛋白质的组成部分，如氨基酸半胱氨酸和蛋氨酸。二甲基亚砜是一种有机硫化合物，在我们的海洋中随处可见，是由一些自然生物和化学过程产生的。DMSO很重要，因为它既是一种叫做二甲基硫醚（DMS）的气候冷却气体的来源，也是一种汇。DMS是海滨气味的一种成分。海洋微生物每年制造约3亿吨二甲硫醚。其中一些二甲基硫被释放到海洋上方的大气中，在那里它在空气中反应成形成云的化合物，这被认为会影响天气和气候。当下雨时，硫化合物沉积回我们大陆的土壤中。然而，在海洋中形成的二甲硫醚大多数被认为不会释放到大气中，而是转化为二甲硫醚，从而留在海水中。然而，这种二甲基亚砜发生了什么在很大程度上仍然是一个谜，但有人认为它可以转化回二甲基硫，从而成为与气候相关的硫排放到大气中的来源。我们所知道的是，二甲基亚砜通常是海洋中最丰富的有机硫化合物，是基本生命元素硫和碳的主要来源。本提案中要进行的研究重点是首先找出DMSO在海水中发生的情况。我们有一些初步的证据，发现使用放射性标记的DMSO作为示踪剂，它被微生物降解，微生物既将其碳纳入其生物质中用于生长目的，又将其降解为二氧化碳。然而，我们也认为，也许其他微生物可以将DMSO转移回DMS，甚至将其硫作为必需元素。因此，在本提案中，我们设计了一系列不同的示踪剂实验，以查明在我们的海洋中发生了哪些过程，它们有多重要以及它们发生的速度有多快。我们还将使用DMSO为微生物命名，并找出涉及哪些代谢途径。我们将在英吉利海峡的L4站研究这些微生物的DMSO转化。该观测站作为西海峡观测站的一部分每周进行一次采样，由普利茅斯海洋实验室协调。这是一个长期存在的时间序列网站，其中还测量了关于浮游植物多样性、丰度、温度、营养动态和细菌多样性的数据，并将免费提供给该项目（www.westernchannelobservatory.org.uk）。鉴于DMSO及其相关化合物DMS的重要作用，确定DMSO从海水中去除的种群和途径将提供关键信息，这将提高我们未来对复杂硫循环及其如何影响气候的理解。

Dimethylsulfoxide (DMSO) is a chemical with a wide range of applications. It is a widely used solvent, for instance in pharmaceutical applications, and a waste product of the paper milling industry. It also occurs naturally in a range of fruits, like raspberries, and vegetables. However, DMSO is also a compound that is part of the natural sulphur cycle. Sulphur is an essential element for all life, and in its organic form is a component of all proteins such as the amino acids cysteine and methionine. DMSO is an organic sulphur compound found everywhere in our oceans, and is produced by a number of natural biological and chemical processes. DMSO is important because it is both a source and a sink for a climate-cooling gas called dimethyl sulfide (DMS). DMS is a component of the smell of the seaside. Around 300 million tons of DMS are made each year by marine microorganisms. Some of this DMS is released into the atmosphere above the oceans, where it reacts in air to compounds that seed clouds, which is suggested influences weather and climate. When it rains, sulphur compounds are deposited back into the soils of our continents. However the majority of the DMS formed in the oceans is thought not to be released to the atmosphere, but rather to be converted to DMSO, and thus stays in seawater. However what happens to this DMSO largely remains a mystery, but it has been suggested that it can be converted back to DMS, and thus be a source for climatically relevant sulphur emissions to the atmosphere. What we do know is that DMSO is commonly the most abundant organic sulphur compound in the oceans, and represents a major pool of the essential life elements sulphur and carbon. The research to be carried out in this proposal is focused on firstly finding out what happens to DMSO in seawater. We have some preliminary evidence, found using radiolabelled DMSO as a tracer, that it is degraded by microorganisms who both incorporate its carbon into their biomass for growth purposes, and degrade it to carbon dioxide. However we also think that perhaps other microbes could transfer DMSO back to DMS, and even use its sulphur as an essential element. Therefore in this proposal we have designed a series of different tracer experiments to find out which processes occur in our seas, how important they are and how fast they happen. We will also put names to the microbes using DMSO, and find out which metabolic pathways are involved. We will study these microbial DMSO transformations in the English Channel at a station called L4. This station 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 data on phytoplankton diversity, abundance, temperature, nutrient dynamics and bacterial diversity are also measured and will be made freely available to this project (http://www.westernchannelobservatory.org.uk). Given the important role of DMSO and its related compound DMS, identifying the populations and pathways of DMSO removal from seawater will provide key information that will improve our future understanding of the complex sulphur cycle and how it influences our climate.