Understanding the biosynthesis of omega-3 long chain polyunsaturates in emiliania huxleyi

埃米利藻（Emiliania huxleyi）是一种具有全球性分布的单细胞钙化（白垩覆盖）微藻，是颗石藻的代表。赫胥黎石藻是海洋中数量最多的颗石藻，对海洋生态系统和全球碳硫循环具有重要影响。大量的沿海和海洋中部的E.huxleyi种群（称为水华）经常突然消失，导致大量方解石流入海底，并形成云状二甲基硫化物进入大气。赫胥黎氏棘球绦虫的脂质分布被用作海洋表面温度变化的替代，在地质时间尺度上，甚至短期的季节性时间尺度。过去的研究已经产生了大量的有关地质历史，气候变化和进化的数据。这种历史性的兴趣和势头一直延续到基因组时代，全基因组序列的测定（不久将公布）和遗传操作工具的持续发展。赫胥黎氏大肠杆菌正在迅速成为海洋世界中与大肠杆菌和沙门氏菌等实验室菌株相当的模式菌株。啤酒。此外，最近鉴定出具有影响脂质谱的天然能力的赫胥黎肠杆菌病毒，表明系统具有以受控方式操纵和裂解的潜力。对E.huxleyi感兴趣的历史原因（如其脂质含量和碳酸钙沉积特性）现在具有在后基因组未来开发的潜力。赫胥黎油中一些最丰富的脂肪酸是欧米伽-3多聚脂肪酸类的成员，其作为一种对预防心血管疾病和人类健康的其他方面很重要的营养品引起了相当大的兴趣。其他脂质有可能用作生物燃料。从海藻中提取脂质并不是一个新的想法，然而，在消费者意识不断提高的时代，必须考虑到与其生产相关的环境影响。这就是来自颗石藻的脂质成为主要候选者的地方：我们有机会开发一种新的系统来生产有用的产品，无论是作为化学原料（生物燃料）和/或营养品（omega-3），同时也从碳循环中去除碳。该项目将调查E.huxleyi系统在不久的将来进行商业开发的潜力。将广泛研究赫胥黎肠球菌菌株的脂质谱，以鉴定具有高度商业价值的脂质（例如，ω-3 LC-PUFA二十二碳六烯酸），并在合适的宿主系统中鉴定和表征参与其合成的基因。还将研究将这些途径转移到转基因植物的潜力。另一个新的目标将是C18高度不饱和的ω-3脂肪酸十八碳五烯酸（18：5，n-3）。这是一种特别丰富的omega-3脂肪酸，也是许多鱼油的次要但重要的成分。我们将首次定义这种脂肪酸的生物合成E. huxleyi。将评估病毒编码的鞘脂生物合成途径的作用，特别强调产生的新型鞘脂的性质及其对细胞生理学和裂解的影响。还将评估病毒用于脂质收获工艺的潜力。具体目标：1.深入表征赫氏艾美耳球虫菌株的脂质谱，以鉴定商业相关脂质。2.赫胥黎肠杆菌脂质生物合成基因的鉴定和分子特征3.评估病毒编码的鞘脂途径在感染期间对赫胥黎艾美耳球虫脂质含量的影响及其对宿主生理学和细胞破坏的影响。4.评估通过异源表达E. huxleyi基因在合适的宿主中。

Emiliania huxleyi is a representative of the cocolithophores, a group of unicellular calcifying (chalk-covered) microalgae with global distribution. E.huxleyi is the most numerous coccolithophore in our oceans and greatly impacts on marine ecosystems and on the global carbon and sulphur cycles. Vast coastal and mid-ocean populations (known as blooms) of E.huxleyi often disappear suddenly causing substantial fluxes of calcite to the seabed and cloud-forming dimethyl sulphide to the atmosphere. E.huxleyi-derived lipid profiles are used as a proxy for variations in sea surface temperature shifts over geological time scales and even short term seasonal time scales. The past study of E.huxleyi has produced a vast amount of data relevant to geological history, climate change and evolution. This historical interest and momentum has followed through to the genomic era with the determination of the full genome sequence (to be released shortly) and the ongoing development of genetic manipulation tools. E.huxleyi is rapidly becoming the marine world's equivalent of model laboratory strains such as E.coli and S. cerevisiae . Furthermore, the recent identification of an E.huxleyi virus with the natural ability to influence the lipid profile, suggests a system that has the potential to be manipulated and lysed in a controlled manner. The historical reasons for interest in E.huxleyi (such as its lipid content and calcium carbonate deposition properties) now have the potential for exploitation in the post-genomic future. Some of the most abundant fatty acids of E.huxleyi are members of the omega-3 polyunsaturate class, which has attracted considerable interest as a nutraceutical, important for the prevention of cardio-vascular disease and other aspects of human health. Other lipids have the potential for use as biofuels. Lipid extraction from marine algae is hardly a new idea, however, in an age of increasing consumer awareness the environmental implications associated with their production must be taken into consideration. This is where lipids derived from the coccolithophores become the leading candidates: we have the opportunity to develop a novel system to produce useful products, either as chemical feedstocks (bio-fuels) and/or nutraceuticals (omega-3s), whilst also removing carbon from the carbon cycle at the same time. This project will investigate the potential of the E.huxleyi system for commercial exploitation in the near future. The lipid profile of E.huxleyi strains will be studied extensively to identify lipids of high commercial interest (for example, the omega-3 LC-PUFA docosahexaenoic acid) and the genes involved in their synthesis identified and characterised in suitable host systems. The potential for transfer of the pathways to transgenic plant will also be investigated. Another novel target will be the C18 highly unsaturated omega-3 fatty acid octadecapentaenoic acid (18:5, n-3). This is a particularly abundant omega-3 fatty acid, and is also a minor yet significant component of many fish oils. We will for the first time define the biosynthesis of this fatty acid in E.huxleyi. The role of the virally encoded sphingolipid biosynthesis pathway will be assessed with particular emphasis on the nature of the novel sphingolipids produced and their effect on cellular physiology and lysis. The potential of the virus to be used in the lipid harvesting process will also be assessed. Specific objectives: 1. In depth characterisation of E.huxleyi strains' lipid profiles with a view to identifying commercially relevant lipids. 2. Identification and molecular characterisation of lipid biosynthesis genes in E.huxleyi. 3. Assess the impact of the virally encoded sphingolipid pathway on E.huxleyi lipid content during infection and its impact on host physiology and cellular disruption. 4. Evaluate the potential for high-value omega-3 fatty acids production via heterologous expression of E. huxleyi genes in a suitable host.