Organisation, dynamics and biogenesis of a photosynthetic membrane

蓝藻是最古老的微生物，通过光合作用以类似于植物的方式生长。蓝藻在地球环境中广泛存在。例如，它们在河流、湖泊和海洋中非常丰富，它们对地球的可持续生态做出了重要贡献。人们对利用蓝藻作为“生物燃料”的可能来源越来越感兴趣。我们或许最终能够改造蓝藻，建造新的人工细胞“工厂”，利用太阳光的能量生产氢等燃料。蓝藻的细胞结构比大多数细菌都要复杂。细胞内部是类囊体膜，这是一个复杂的内部膜系统，是光合作用“光反应”的场所。类囊体膜含有从阳光中吸收能量的色素和将太阳能转化为储存的化学能的第一步的蛋白质。虽然我们现在对光合作用蛋白模块有了大量的了解，但我们对自然界中类囊体膜是如何产生的知之甚少。我们建议使用一种“模型”蓝藻来研究这个问题，这种蓝藻可以很容易地进行基因改造，并且具有规则形状的类囊体膜。我们将首先控制蓝藻细胞产生类囊体膜的能力。通过切换细胞中类囊体膜的生成，并用荧光标记光合蛋白，我们将能够使用光学显微镜详细观察在膜构建过程中蛋白质是如何合成并整合到类囊体膜中的。为了更详细地了解光合作用蛋白在类囊体膜中的分布情况，我们将使用高分辨率显微镜扫描类囊体膜表面，以确定类囊体膜发育过程中单个蛋白及其位置。该计划的第二部分是研究光合蛋白如何在类囊体膜中相互作用，这对它们的能量转导功能很重要。为此，我们将用不同的荧光标签标记蛋白质，并观察不同的蛋白质如何在细胞中移动和与其他蛋白质组装。我们还将从细胞中纯化蛋白质复合物，并使用生化技术检查这些复合物的蛋白质组成。此外，我们还将通过从不同发育阶段分离的类囊体膜中提取脂质并鉴定脂质组成和含量，了解脂质分子在类囊体膜的形成和功能中所起的作用。如果我们能对类囊体膜是如何组装的有更深入的了解，我们就能更好地修改类囊体膜的功能，例如，从太阳能中产生氢。从长远来看，我们甚至可以在不同种类的细菌中诱导类似的膜系统的产生，从而为微生物“细胞工厂”的产生提供新的工具。

Cyanobacteria are the oldest microorganisms that grow by photosynthesis in a similar way to plants. Cyanobacteria are widespread in our environment on Earth. For example, they are very abundant in rivers, lakes, and the oceans, and they make important contributions to the sustainable ecology of the planet. There are increasing interests in using cyanobacteria as possible sources of 'biofuels'. We may eventually be able to modify cyanobacteria to build new artificial cell "factories" that can use the energy of sunlight to produce fuels such as hydrogen. Cyanobacteria have a more complex cell structure than most bacteria. Inside the cells are the thylakoid membranes, a complex internal membrane system which is the site of the 'light reactions' of photosynthesis. The thylakoid membranes contain the pigments that absorb energy from sunlight and the proteins that carry out the first steps in converting solar energy to stored chemical energy. Although we now have a great deal of knowledge about the photosynthetic protein modules, we know rather little about how the thylakoid membranes are generated in nature. We propose to investigate this question using a 'model' cyanobacterium that can easily be genetically modified and have a regular shape of thylakoid membranes. We will first control the ability of cyanobacterial cells to produce thylakoid membranes. By switching the generation of thylakoid membranes in the cell and tagging the photosynthetic proteins with fluorescence, we will be able to watch in detail how proteins are synthesised and integrated into the thylakoid membrane during the membrane construction process using optical microscopy. To get more details on how the photosynthetic proteins are distributed in the thylakoid membrane, we will use a high-resolution microscope to scan the thylakoid membrane surface in order to determine individual proteins and their locations during the development of thylakoid membranes. The second section of this programme is to study how photosynthetic proteins interact with each other in the thylakoid membrane, which is important for their energy-transducing functions. For this purpose, we will label the proteins with different fluorescent tags and watch how different proteins move and assemble with others in the cell. We will also purify the protein complexes from cells and examine the protein composition of these complexes using biochemical techniques. Furthermore, we will also learn how the lipid molecules play roles in the formation and function of the thylakoid membrane, by extracting the lipids from the thylakoid membranes isolated from different development stages and identifying the lipid composition and content. If we can gain advanced understanding as to how thylakoid membranes are assembled we will be in a better position to modify the thylakoid membrane function, for example, to produce hydrogen from solar energy. In the long-term we may even be able to induce the production of similar membrane systems in different kinds of bacteria, giving us a new tool for the generation of microbial 'cell factories'.