NI: Microbial Dimethylsulphide Degradation in Anoxic Baltic Sea Sediments

甲烷是一种强大的温室气体，它对全球变暖起到了重要作用。这种气体是由生活在缺氧(缺氧)环境中的微生物产生的。我们知道海洋环境产生大量甲烷已经有一段时间了。然而，海洋生态系统中甲烷的来源还没有得到充分的描述，这是正确计算这些环境中甲烷排放量的障碍。特别是，我们对哪些微生物产生甲烷以及它们使用什么代谢过程知之甚少。以前的研究表明，微生物可以利用二甲基硫化物(DMS)来生长和产生甲烷。二甲基硫是一种气体，在海洋环境中可以发现浓度很高的气体。这些栖息地中的DMS是通过另一种名为DMSP的化合物分解而产生的，这种化合物在浮游植物大量繁殖后大量释放。波罗的海是一个独特的环境。这是因为它是世界上最大的微咸水(中低盐度)海域之一。它还经常受到浮游植物水华的影响。总体而言，波罗的海为研究DMS的使用和微生物产生甲烷提供了一个极好的天然实验室。波罗的海的咸水状况尤为重要。因为，硫酸盐是决定盐度的重要离子之一。低到中等的盐度意味着微生物可以利用硫酸盐。然而，这可能会影响产生甲烷的微生物的活动。这是因为甲烷生产商与硫酸盐使用者争夺碳源，在我们的案例中是DMS。根据这种相互作用的结果，海洋沉积物中产生的甲烷数量可能会显著减少。因此，我们的目标是了解这一代谢途径是如何工作的，以及哪些微生物负责这一过程。为了实现我们的目标，我们与来自瑞典的同事建立了新的伙伴关系，他们在波罗的海研究和使用强大计算设施分析关键数据的工具方面拥有长期经验。我们将使用我们新颖的微生物生态学方法，将最先进的技术与称为高通量测序的先进微生物鉴定工具相结合。首先，我们将确定DMS在多大程度上有助于缺氧的、微咸水的波罗的海沉积物中甲烷的产生。然后我们将使用同位素标记的DMS，这使我们能够追踪沉积物中碳的命运。然后，我们将使用标记的沉积物样本中微生物的遗传物质(DNA和RNA)来识别使用DMS(产生甲烷或使用硫酸盐)的微生物，并推断它们的新陈代谢。结果将告诉我们通过DMS产生甲烷的数量，哪些微生物使用DMS并产生甲烷，以及它们如何在波罗的海沉积物的微咸水条件下进行这一过程。总体而言，该项目的成果将极大地提高我们对海洋沉积物中甲烷产量的理解，并有助于通过改进的气候模型计算温室气体预算。这最终将帮助我们应对全球变暖和气候变化。

Methane is a powerful greenhouse gas which significantly contributes to global warming. This gas is produced by microbes that live in environments that lack oxygen (anoxic). We have known for some time that marine environments produce substantial amounts of methane. However, the sources of methane in marine ecosystems have not been fully described, which is a barrier to correct calculation of methane emissions from these environments. In particular, we know very little about which microbes produce methane and what metabolic process they use.Previous studies showed that microbes can use dimethylsulphide (DMS) to grow and produce methane. DMS is a gas, which can be found in very high concentrations in marine environments. DMS in these habitats is produced through the breakdown of another compound shortly called DMSP, which is released in huge amounts following a phytoplankton bloom. The Baltic Sea is a unique environment. This is because it is one of the largest brackish (moderate to low salinity) seas in the world. It is also subjected to regular phytoplankton blooms. Overall, the Baltic Sea provides an excellent natural laboratory to study DMS use and methane generation by microbes. The brackish condition of the Baltic Sea is particularly important. Because, sulphate is one of the important ions that determine the salinity. Low-to-moderate salinity means there is sulphate available to microbes. This may however affect the activity of methane-producing microbes. This is because methane-producers compete with sulphate-users for carbon sources, in our case for DMS. Depending on the outcome of this interaction, the amount of methane produced in marine sediments may reduce significantly. Therefore, we aim to understand how this metabolic pathway works and which microbes are responsible of this process. In order to achieve our aim, we initiate a new partnership with colleagues from Sweden, who have long-term experience in the Baltic Sea research and tools to analyse critical data using powerful computing facilities. We will use our novel microbial ecology approach that combines state-of-the-art techniques with advanced microbial identification tools called high-throughput sequencing. Firstly, we will determine the extent to which DMS contributes to methane production in anoxic, brackish Baltic Sea sediments. We will then use isotopically labelled DMS, which enables us to follow the fate of carbon in sediments. Then, we will use genetic material (DNA and RNA) from microbes in the labelled sediment samples to identify the microbes that use DMS (methane-producing or sulphate-using) and infer their metabolism. The results will tell us the magnitude of methane production via DMS, which microbes use DMS and produce methane and how they carry out this process in brackish conditions in the Baltic Sea sediments. Overall, the outcome of this project will greatly improve our understanding of methane production in marine sediments and help in calculating greenhouse gas budgets via improved climate models. This will ultimately help us tackling global warming and climate change.