Fast DMS Sensor for online quantification of dimethyl sulphide (DMS)

二甲基硫化物(DMS)是海洋环境中产生的一种痕量气体，给海洋带来了典型的“海洋气味”。多年来，人们一直在监测海水和空气样本中的DMS浓度，因为研究表明，DMS负责在遥远的海洋大气中形成云。当然，这对于我们对气候和未来全球变化的理解很重要。与这种全球意义形成对比的是，我们对DMS是如何、何时以及为什么产生的知之甚少。大多数DMS是从二甲基磺酸碘丙酸酯(DMSP)中酶解出来的，DMSP是一种许多藻类用作渗透调节剂的化合物，用于在高盐环境中生存。传统的海水和空气中二甲基硫的定量方法(吹扫捕集与气相色谱联用)既费时又费力。因此，我们目前缺乏在藻类养殖中生产二甲基硫的高分辨率数据。我们假设DMS的产量在一天中是可变的，并且对环境胁迫(如高光条件)很敏感。利用化学发光检测DMS在空气中进行高分辨率测量的方法已经存在，但这项技术尚未被用于解决水中DMS生产的生理问题。我们在水和曝气恒化器培养的废气中进行了DMS测量，这些培养物是全球重要的产生DMS的埃米利亚尼亚藻类。曝气有效地将大部分二甲基硫从水中清除出来，并将这些气体转移到气流中。因此，废气中的DMS浓度提供了DMS生产的准确测量。由于废气中DMS的浓度相对较高(百万分之2至40ppm)，而其他痕量气体的浓度相对较低，因此可以使用DMS的臭氧诱导化学发光来连续监测这种化合物的浓度。我们已经测试了一种商用的化学发光检测器(快速异戊二烯传感器)，发现DMS在百万分之几到百万分之几的浓度范围内与DMS呈线性关系。这是令人鼓舞的，并表明该仪器可以很容易地用于我们的应用。我们建议优化和测试用于DMS测量的快速异戊二烯传感器。使用连续培养的E.huxleyi的化学恒化器的一系列实验将被用于在稳定条件下处理DMS的产生，然后以短时间的光强度增加(在可见光和紫外光谱中)来干扰系统。光照已被证明影响湖北龙须草DMS的产生，DMS被认为是一种抗氧化剂，并有助于清除在强光条件下产生的有害活性氧物种。然而，DMS在这种胁迫条件下的生产动态尚不清楚。我们的项目将提供有关E.Huxleyi DMS生产的新信息。它将进一步测试一种在线化学发光检测器，用于廉价的连续监测藻类培养中DMS的产生。我们预计，这种高分辨率的方法将用于未来的赠款申请，以解决从各种生物，包括其他浮游植物物种、大型藻类、真菌和细菌产生DMS的问题。

Dimethyl sulphide (DMS) is a trace gas produced in marine environments that gives the ocean the typical 'smell of the sea'. Its concentrations in seawater and in air samples have been monitored for many years, since research demonstrated that DMS is responsible for making clouds in the remote marine atmosphere. Of course, this is important for our understanding of climate and future global change. In contrast to this global significance, we know very little about how, when and why DMS is produced. Most of the DMS is enzymatically cleaved from dimethylsulphoniopropionate (DMSP), a compound that many algae use as an osmolyte to survive in high salt environments. Conventional methodology (purge-and-trap coupled to gas chromatography) to quantify DMS in seawater and air is laborious and time-consuming. As a result, we currently lack high-resolution data on the production of DMS in algal cultures. We hypothesise that DMS production is variable over the day and sensitive to environmental stress such as high light conditions. Methodology using chemiluminescence detection of DMS for high resolution measurements in air exists but this technology has not been used to address physiological aspects of DMS production in water. We conducted DMS measurements in the water and in the waste air from aerated chemostat cultures of the globally important and DMS-producing alga Emiliania huxleyi. The aeration efficiently purges most of the DMS out of the water and transfers this gas into the air stream. As a result, the DMS concentrations in the waste air provide an accurate measurement of DMS production. Since the DMS concentrations in the waste air are relatively high (2 to 40 parts per million) and other trace gases occur at relatively low concentrations, it is possible to use the ozone-induced chemiluminescence of DMS to continuously monitor the concentration of this compound. We already tested a commercially available chemiluminescence detector (Fast Isoprene Sensor) for DMS and found a linear response to DMS in the parts per billion to parts per million concentration range. This is encouraging and suggests that this instrument could be readily used for our application. We propose to optimise and test the Fast Isoprene Sensor for our DMS measurements. A series of experiments using chemostats with continuous cultures of E. huxleyi will be used to address DMS production under steady-state conditions before perturbing the system with short periods of increased light intensity (in the visible and ultraviolet spectrum). Light has been shown to affect DMS production in E. huxleyi, and it is thought that DMS functions as an antioxidant and assists with the removal of harmful reactive oxygen species that are produced under high light conditions. However, the dynamics of DMS production under such stressful conditions are unknown. Our project will deliver new information on DMS production in E. huxleyi. It will further test an online chemiluminescence detector for inexpensive continuous monitoring of DMS-production in algal cultures. We envisage that this high-resolution methodology will be used in future grant applications that will address DMS-production from various organisms including other phytoplankton species, macroalgae, fungi and bacteria.