Influence of inorganic carbon and mutations in carbon-regulated pathways on metabolite pools and turnover in cyanobacteria

光自养细胞中基本碳代谢的一般方案早在几十年前就已为人所知。然而，已完成的基因组测序项目显示，关键途径的酶缺失，或者这些途径在不同的生物体中似乎是可变组织的。只有很少有人研究代谢物通过相互作用和竞争的途径网络的流量。利用蓝藻菌株聚球藻。PCC6803作为一个简单的模型，我们想要分析光合作用有机体中的碳流，而不是隔室。功能分析的主要工具将是代谢物库大小变化的代谢组研究和利用基于GC-TOF-MS的代谢物图谱平台的稳定同位素示踪剂研究。该生物体将在不同的碳水平下培养，并将包括在关键途径上出现缺陷的突变株。尤其令人感兴趣的是对假定的光呼吸突变的分析，这是一种与光合作用密切相关的途径，但其作用尚不清楚，尤其是在蓝藻中。光呼吸循环的主要功能似乎是将2-磷酸乙醇酸转化为3-磷酸甘油酸，并被发现在环境CO2浓度下对植物是必需的。相反，在蓝藻中，相应基因中的突变被发现是可行的，这表明存在补偿途径。代谢组分析将给出可能涉及哪些途径的线索。这些结果将提高我们对光自养碳代谢的认识，并可能在未来用于优化植物的光合作用。

The general scheme of basic carbon metabolism in photoautotrophic cells is known since decades. However, finished genome sequencing projects revealed that enzymes of key pathways are missing or such pathways seem to be variable organized in different organisms. Only scarcely investigated is the flux of metabolites through the network of interacting and competing pathways. Using the cyanobacterial strain Synechocystis sp. PCC 6803 as a simple model we want to analyze the carbon flow in a photosynthetic organism without compartmentation. The main tool of functional analysis will be metabolome studies of changes in metabolite pools size and stable isotope tracer studies utilizing GC-TOF-MS based metabolite profiling platform. The organism will be cultivated at different carbon levels and mutants showing defects in key pathways will be included. Particularly interesting will be the analysis of putative photorespiratory mutants, a pathway closely linked to photosynthesis but not well understood in its role especially in cyanobacteria. The main function of the photorespiratory cycle seems to be the conversion of 2-phophoglycolate to 3- phosphoglycerate and was found to be essential for plants at ambient CO2 concentration. In contrast, in cyanobacteria mutants in corresponding genes were found to be viable, which indicates that compensating pathways exist. The metabolome analyses will give hints, which pathways may be involved. Such results will improve our knowledge of photoautotrophic carbon metabolism and may be used to optimize plant photosynthesis in the future.