DiMethylSulfonioPropionate cycling In Terrestrial environments (DMSP InTerrest)

仅在地球表面的海洋中，海洋微生物和植物每年就通过我们已经确定的酶产生80亿吨二甲基磺基丙酸盐（DMSP）。生物产生DMSP以保护免受盐、冷、膨压、氧化和干旱胁迫以及捕食。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素。DMSP在全球硫和碳循环、信号传导中发挥着至关重要的作用，并且是二甲基硫（DMS）和恶臭气体甲烷乙烷（MeSH）等气候活性气体（CAG）的主要来源。每年有数百万吨二甲基硫醚（DMS）通过微生物DMSP裂解酶从DMSP中释放出来，二甲基硫醚是海滨特有的气味，也是引导各种生物（海鸥、海豹、浮游动物等）寻找食物的有力觅食线索。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，减少全球辐射收支和“冷却”当地气候。至关重要的是，这些硫酸盐气溶胶通过雨水返回陆地--这是生物硫从海洋到陆地的主要转移。DMSP的合成和降解被认为只发生在海洋环境中，所以DMSP在陆地环境中的循环在很大程度上是unexplored.We挑战这一教条，揭示了DMSP的合成是广泛存在于植物王国，从常见的植物，如草，农业上重要的作物，如玉米，卷心菜和甘蔗。此外，我们的初步工作表明，DMSP水平超过海水中存在于这些关键农业和生物能源作物生长的土壤中。我们的工作表明，这样的土壤释放出大量的DMS和MeSH -气候模型中忽略的过程。我们还从玉米和甘蔗土壤中分离出了新的细菌和真菌，它们利用DMSP作为碳源，并显示出可诱导的DMSP依赖性DMS或MeSH生产。重要的是，这些细菌在其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的和几乎未开发的研究领域与地球化学循环的深远影响。我们的研究结果迫切需要详细的研究，以建立陆地DMSP循环对气候的重要性和影响，我们希望回答的根本重要问题，微生物如何与陆地植物降解DMSP，以及生态和全球的重要性的过程，特别是与CAG生产。我们将测试植物制造的DMSP是产生CAG的微生物的关键营养素的假设。在日常生活中，降解DMSP的微生物是卷心菜田的腐烂MeSH气味的罪魁祸首，还是甜玉米的甜DMS气味的罪魁祸首？我们将研究与已知产生低（玉米）和高（甘蔗）DMSP水平的植物相关的微生物DMSP降解和伴随的CAG生产，这些植物的总面积超过2亿公顷。合作已经到位，以采样这些植物，因为是模型DMSP生产细菌，我们分离研究微生物DMSP降解机制在陆地环境中。我们的主要目标是阐明陆地微生物中DMSP降解的酶、途径和机制，并利用这些知识来确定该过程的规模和调控因素。此外，我们将利用尖端的微生物生态学、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和释放CAG的关键微生物是什么，它们如何影响气候？我们认为我们的提案是为了应对一个重大的新挑战，它将揭示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产生深远的影响。

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.