Microbial Control of Carbon Fixation

地球上大约三分之一的光合作用是由水生细菌完成的。在细胞内没有膜结合区室的情况下，这些生物通过将碳固定酶紧密包装在称为羧基体的蛋白质区室中，为碳固定酶创造了有利的环境。尽管羧基体对全球碳循环的重要性及其作为合成生物学平台的潜力，但羧基体组装过程仍然知之甚少。这项研究将阐明的分子机制，指定的大小，数量和内部环境的羧基体。它将融合生物化学方法，合成生物学和荧光显微镜来探索整个carboxysomes随着时间的推移组装过程，并将此过程置于细胞生理学的背景下。对羧基体形成的基本生物学机制的理解将为这些隔间的未来工程奠定基础。为此，该项目将进一步推动NSF的使命，即扩大科学和工程研究潜力，无论是通过改善天然碳固定还是为活细胞内的其他敏感化学反应建立纳米级工厂。该项目还将提供一个理想的跨学科教育和培训计划。更广泛地说，羧基体工作的最终目标是改善新功能的工程。这种合成的类生命系统可以被赋予隔离和包含与细菌细胞质不相容的反应的能力，或者改善碳固定以产生更有效的二氧化碳的活修复剂。减少大气中二氧化碳的含量将阻止气候变化，从而带来重大的社会效益。随着大气中二氧化碳含量接近400 ppm，了解碳固定的生物机制变得越来越重要。大部分的二氧化碳是由光合蓝藻修复的，它将固定碳所需的机器集中到称为羧基体的蛋白质微区室中。在细长聚球藻中，这些细胞器由围绕酶RuBisCO和碳酸酐酶基质的一层壳蛋白组成。尽管它们对全球碳循环很重要，但控制这些复杂蛋白质机器组装的因素却知之甚少。哈佛医学院的Pamela银博士和她的团队将采用生化重建、遗传扰动和定量活细胞显微镜来研究羧基体生物发生的空间和时间组织的分子基础和代谢后果。

Approximately one third of all the photosynthesis on earth is performed by aquatic bacteria. In the absence of membrane-bound compartments inside their cells, these organisms create a favorable environment for carbon-fixing enzymes by tightly packaging them inside protein compartments called carboxysomes. Despite the importance of carboxysomes to the global carbon cycle and their potential to serve as a platform for synthetic biology, the carboxysome assembly process is still poorly understood. This research will elucidate the molecular mechanisms specifying the size, number, and internal environment inside carboxysomes. It will blend biochemical approaches, synthetic biology, and fluorescence microscopy to explore the assembly process of whole carboxysomes over time, and to place this process in the context of cellular physiology. An understanding of the basic biological mechanisms by which carboxysomes are formed will lay the groundwork for future engineering of these compartments. Toward this end, this project will further the NSF's mission of expanding science and engineering research potential, whether by improving on natural carbon fixation or building nanoscale factories for other sensitive chemical reactions within living cells. This project will provide also an ideal interdisciplinary educational and training program. More broadly, the ultimate goal of the carboxysome work is to improve the engineering of novel functionalities. Such a synthetic life-like system could be endowed with the ability to sequester and contain reactions otherwise incompatible with the bacterial cytoplasm, or improve upon carbon fixation to create more efficient, living remediators of carbon dioxide. Reducing the levels of atmospheric carbon dioxide, a major greenhouse gas, would forestall climate changes, and therefore offer major societal benefit.As atmospheric carbon dioxide levels are approaching 400 ppm, understanding biological mechanisms of carbon fixation is becoming increasingly important. A large fraction of carbon dioxide is remediated by photosynthetic cyanobacteria, which concentrate the machinery required to fix carbon into proteinaceous microcompartments called carboxysomes. In Synechococcus elongatus, these organelles, are composed of a layer of shell proteins surrounding a matrix of the enzymes RuBisCO and carbonic anhydrase. Despite their importance to the global carbon cycle, the factors controlling assembly of these complex protein machines are poorly understood. Dr. Pamela Silver and her group at the Harvard Medical School will employ biochemical reconstitution, genetic perturbations, and quantitative live-cell microscopy to study the molecular basis and metabolic consequences of the spatial and temporal organization of carboxysome biogenesis.