DiMethylSulfonioPropionate cycling In Terrestrial environments (DMSP InTerrest)

仅在地球表层海洋中，生活在海洋中的微生物和植物每年就会通过我们已经确定的酶产生80亿吨二甲基磺酸丙酸酯(DMSP)。生物体产生DMSP以抵御盐度、寒冷、膨胀压力、氧化和干旱压力以及捕食。释放到环境中的DMSP也因这些抗应激特性而被微生物广泛吸收，并通过不同的降解途径用作关键营养物质。DMSP在全球硫和碳循环、信号传递以及作为气候活性气体(CAG)(如二甲基硫化物(DMS)和恶臭气体甲硫醇(MESH))的主要来源方面发挥着至关重要的作用。每年数百万吨的DMS，海边特有的气味和引导不同生物(海鸥、海豹、浮游动物等)觅食的有力线索，通过我们也鉴定的微生物DMSP裂解酶从DMSP释放出来。一些二甲基硫被释放和氧化，在大气中形成气溶胶和云凝结核，这减少了全球辐射收支，并使当地气候变冷。至关重要的是，这些硫酸盐气溶胶在降雨中返回陆地--这是生物硫从海洋向陆地的主要转移。DMSP的合成和降解被认为只发生在海洋环境中，所以在陆地环境中的DMSP循环在很大程度上还没有被开发。我们通过揭示DMSP的合成在植物界广泛存在，从常见的植物如草，到农业上重要的作物如玉米、甘蓝和甘蔗，我们对这一教条提出了挑战。此外，我们的初步工作表明，在这些主要农业和生物能源作物生长的土壤中，DMSP水平超过了海水中的水平。我们的工作表明，这样的土壤释放了大量的DMS和气候模型中被忽视的网格过程。我们还从玉米和甘蔗土壤中分离出了新的细菌和真菌，这些土壤利用DMSP作为碳源，并显示出可诱导的依赖于DMSP的DMS或Mesh生产。关键是，这些细菌的基因组中缺乏已知的DMSP降解基因，因此可能具有新的DMSP分解代谢酶和/或途径。因此，我们发现了一个潜在的大而几乎未探索的研究领域，对生物地球化学循环具有深远的影响。我们的发现迫切需要详细的研究来确定陆地DMSP循环对气候的重要性和影响。我们希望回答与陆地植物相关的微生物如何降解DMSP的根本重要问题，以及该过程的生态和全球重要性，特别是与CAG生产相关的问题。我们将检验这一假设，即植物制造的DMSP是产生CAG的微生物的关键营养物质。在日常生活中，降解DMSP的微生物是与卷心菜田有关的腐烂网状气味还是与甜玉米有关的DMS甜味？我们将研究微生物对DMSP的降解以及与已知产生低水平(玉米)和高水平(甘蔗)DMSP的植物相关的CAG生产，这些植物总共覆盖了2亿公顷土地。我们已经开始合作对这些植物进行采样，我们分离的产生DMSP的细菌模型也是如此，以研究微生物在陆地环境中的降解机制。我们的主要目标是阐明DMSP在陆地微生物中降解的酶、途径和机制，并利用这一知识来定义这个过程的规模和调节它的因素。此外，我们将使用尖端微生物生态学、建模和过程工作来回答基本的生态学问题：在陆地环境中降解DMSP并释放CAG的关键微生物是什么，以及它们如何影响气候？我们认为我们的提议是为了应对一个重大的新挑战，这将揭示DMSP在陆地环境中的重要性，揭示新的和意想不到的研究领域，对当前和未来的气候模型具有深远的影响。

Marine-dwelling microbes and plants produce 8 billion tonnes of dimethylsulfoniopropionate (DMSP) per year in Earth's surface oceans alone, via enzymes we have identified. Organisms produce DMSP to protect against salinity, cold, turgor pressure, oxidative and drought stresses, and predation. DMSP released into the environment is also widely taken up by microbes for these anti-stress properties, and used as a key nutrient via distinct degradation pathways. DMSP has critically important roles in global sulfur and carbon cycling, signalling, and as a major source of climate-active gases (CAG) e.g. dimethylsulfide (DMS) and the foul-smelling gas methanethiol (MeSH). Each year millions of tonnes of DMS, the characteristic smell of the seaside and a potent foraging cue guiding diverse organisms (gulls, seals, zooplankton, etc) to food, is released from DMSP via microbial DMSP lyase enzymes that we also identified. Some DMS is released and oxidised to form aerosols and cloud condensation nuclei in the atmosphere, which reduce the global radiation budget and 'cool' local climate. Critically, these sulfate aerosols return to land in rain - the primary transfer of biogenic sulfur from the oceans to land. DMSP synthesis and degradation are thought to occur only in marine settings, so DMSP cycling in terrestrial environments has largely been unexplored.We challenged this dogma by revealing that DMSP synthesis is widespread in the plant Kingdom, ranging from common plants like grass, to agriculturally-important crops like maize, cabbage and sugarcane. Furthermore, our preliminary work shows that DMSP levels surpassing those in seawater exist in soils in which these key agricultural and bioenergy crops grow. Our work shows such soils liberate significant quantities of DMS and MeSH - processes ignored in climate models. We have also isolated novel bacteria and fungi from maize and sugarcane soils that utilise DMSP as a carbon source and show inducible DMSP-dependent DMS or MeSH production. Critically, these bacteria lack known DMSP degradation genes in their genomes, and thus likely possess novel DMSP catabolic enzymes and/or pathways. We have therefore uncovered a potentially large and virtually unexplored research area with profound implications for biogeochemical cycling. Our findings urgently require detailed study to establish the importance and influence of terrestrial DMSP cycling on the climate.We wish to answer the fundamentally important questions of how microbes associated to terrestrial plants degrade DMSP, and the ecological and global importance of the process, especially relating to CAG production. We will test the hypothesis that plant-made DMSP is a key nutrient for CAG-producing microbes. In an everyday context, are microbes degrading DMSP responsible for the rotten MeSH smell associated with cabbage fields, or the sweet DMS smell associated with sweetcorn? We will study microbial DMSP degradation and concomitant CAG production associated to plants known to produce low (maize) and high (sugarcane) levels of DMSP, which together cover >0.2 billion ha. Collaborations are in place to sample these plants, as are the model DMSP-producing bacteria we isolated to study microbial DMSP degradation mechanisms in terrestrial environments. Our major aims are to elucidate the enzymes, pathways, and mechanisms of DMSP degradation in terrestrial microbes and use this knowledge to define the magnitude of the process and factors regulating it. Furthermore, we will use cutting-edge microbial ecology, modelling and process work to answer fundamental ecological questions: what are the key microbes that degrade DMSP and emit CAG in terrestrial environments, and how do they influence the climate?We see our proposal as addressing a major new challenge that will reveal the importance of DMSP in terrestrial environments, uncovering new and unexpected research fields with far-reaching implications for current and future climate models.