Biosynthesis, Regulation and Engineering of Bacterial Carbon Fixation Machinery

单细胞蓝藻是地球上最丰富的生物之一。它们创造并帮助维持了我们的大气，估计占当前全球碳固定的20%-30%。为了加强碳固定，蓝藻形成称为羧基体的小隔间，以吸收二氧化碳，并通过光合作用将其转化为化学能。这些高效的机器在结构上由外层以蛋白质为基础的外壳和内部高度集中的二氧化碳固定酶定义。壳层由许多不同的蛋白质组成，是特定分子进出隔间的选择性“屏障”。当前，全球粮食和能源安全问题备受关注。我们如何才能改善粮食供应，以跟上世界人口的步伐？我们如何才能为粮食和能源生产开发环境可持续的解决方案？合成羧体的生产和工程并将其引入其他生物体，特别是植物，在改善光合作用、固碳和作物产量方面具有巨大的潜力。由于蓝藻在进化上与植物叶绿体非常接近，从蓝藻中学到的经验教训将对植物科学和工程非常有用。合成生物学的最新发展提供了必要的策略和方法，为制造人造生物机器打开了大门。然而，在其他生物中产生功能羧体需要全面了解它们在其自然宿主蓝藻中的发育和生理调节。这个项目的目的是全面阐明蓝藻细胞如何创建这些特殊的隔室，它们的活动如何在细胞内动态调节以适应不断变化的环境，以及这些机器如何与细胞内整个新陈代谢网络中的其他细胞活动一起工作。在这个研究项目的第一部分，我们将使用一种特殊的光学显微镜来观察活细胞中羧酸体的发育和分布，并研究这些细胞器在不同环境条件下生长的细胞内是如何调节的。第二部分将描述这些细胞器如何与其他细胞成分相互作用和发挥作用，以实现其代谢性能。接下来，我们将了解多种蛋白质是如何组织起来的，以构建细胞器的形状。我们将开发一个计算机程序来建立隔间的模型，并模拟蛋白质动力学和分子进出隔间的通道。深入了解从这三个部分衍生的隔室结构、功能和调节，对于具有适当功能的新型生物机器的基因工程非常重要。在最后一节中，我们将利用从蓝藻细胞中学到的知识来合成具有固碳活性的人工生物机器。这项工作为研究细胞内复杂生物机器的发展提供了一个模型。它将教会我们成千上万的蛋白质如何自己组装在一起，形成细胞内的一个功能实体，以及细胞制定了什么调控策略来领导这些机器的发展和功能。在翻译方面，这项工作将为特定细胞活动和生理的新型生物“工厂”的设计和工程提供一个有指导意义的范例。如果我们能够进行基因工程，使高等植物能够开发出合成的蓝藻固碳机器，这将显著提高食物和能源的产量。

The single-cell cyanobacteria are among the most abundant organisms on earth. They created and help to sustain our atmosphere, and account for an estimated 20-30 % of current global carbon fixation. To enhance carbon fixation, cyanobacteria develop small compartments, called carboxysomes, to absorb carbon dioxide and transform it to chemical energy by the process named photosynthesis. These highly efficient machines are structurally defined by an outer protein-based shell and internal highly concentrated CO2-fixing enzymes. The shell is composed of many distinct proteins, and serves as a selective "barrier" for the passage of specific molecules into and out of the compartments. At present, there are great concerns over global food and energy security. How can we improve the food supply to keep pace with the world population? How can we develop environmentally sustainable solutions for food and energy production? Producing and engineering of synthetic carboxysomes and introducing them into other organisms, particularly plants, has significant potential for improving photosynthesis, carbon sequestration and crop yield. As the cyanobacteria is evolutionarily close to the plant chloroplast, lessons learned from the cyanobacteria will be very informative to plant sciences and engineering. Recent developments in synthetic biology have opened the door to generating artificial biological machines by providing the necessary strategies and approaches. However, producing functional carboxysomes in other organisms requires comprehensive knowledge about their development and physiological regulation in their natural hosts, the cyanobacteria. The aims of this project are to elucidate comprehensively how cyanobacterial cells create these specialised compartments, how their activities are dynamically regulated within the cells in response to the changing environment, and how these machines function together with other cellular activities in the entire metabolic network within cells. In the first part of this research project, we will use a special optical microscopy to watch the development and distribution of carboxysomes in living cells, and study how these organelles are regulated within the cells grown under different environmental conditions. The second section will characterise how these organelles interact and function together with other cellular components to achieve their metabolic performance. Next we will find out how multiple proteins are organised in order to build the organelle shape. We will develop a computer programme to build a model of the compartment and simulate the protein dynamics and passage of molecules in and out of the compartment. Advanced understanding of the compartment structure, function and regulation derived from the three sections is important for genetic engineering of novel biological machines with appropriate functionality. In the last section, we will use the knowledge learned from the cyanobacterial cells to synthesise artificial biological machines with carbon fixation activities.This work represents a model for studying the development of complex biological machines within cells. It will teach us about how thousands of proteins can assemble together by themselves to form a functional entity within cells, and what regulatory strategies are developed by the cells to lead the development and function of these machines. In translational terms, this work will provide an instructive example for the design and engineering of novel biological "factories" for specific cellular activities and physiology. If we can conduct genetic engineering to enable higher plants to develop synthetic cyanobacterial carbon-fixing machines, it will significantly enhance food and energy production.