极端嗜盐古菌是一类独特的极端微生物资源，广泛分布于盐湖、海水盐场和盐碱土壤等各种高盐环境。我们前期研究表明，嗜盐古菌具有将CO2固定到胞内聚合物如“聚羟基丁酸羟基戊酸共聚酯（PHBV）”中进行贮存的能力，显示嗜盐古菌在高盐环境碳循环中具有独特而重要的作用。本项目以具有高效PHBV合成能力的地中海富盐菌为主要研究对象，从基因组代谢网络、关键途径、关键基因、调控及适应机制等多个层面系统研究该类海洋嗜盐古菌的固碳和贮碳功能，重点揭示嗜盐古菌同化CO2、乙酸和丙酸等简单碳源的关键途径，解析嗜盐古菌同化乙酰/丙酰-CoA并偶联CO2固定的关键酶类及其生理生化与分子生物学特征，探讨嗜盐古菌将环境中各种碳源贮存为PHBV的生理生态学意义及对高盐环境的适应机制，为认识和利用极端环境条件下微生物驱动地球碳循环的基本机制提供前沿基础。

Halophilic archaea thrive in hypersaline environments, such as the world-wide distributed salt lakes, sea salterns, saline soils and subterranean salt formations. Our previous research shows that many halophilic archaea are capable of accumulating a large amount of poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) in the presence of excess carbon sources, and we also found that CO2 can be fixed into PHBV for storage, indicating that halophilic archaea play unique and important roles in carbon cycling in hypersaline environments. This project selects the Haloferax mediterranei, a haloarchaeon with high efficiency of PHBV synthesis, as one of the primary research objects. The function and mechanism of carbon fixation and storage by this haloarchaeon will be investigated systematically from metabolism network, specific pathways, key genes, to the regulation and adaptation mechanisms, using multifaceted experimental approaches. This project will focus on elucidation of the pathways responsible for assimilation of acetyl-CoA and propionyl-CoA, especially the coupled CO2 fixation, as well as the related PHBV accumulation and mobilization. This project is expected to provide novel insights into the physiological and ecological significance of the relevant carbon assimilation pathways in haloarchaea, and shed new lights on the mechanism of microbially driven carbon cycling in extreme environments.