自养微生物在土壤中广泛存在，但目前对农田与自然土壤自养微生物固碳速率及其功能种群差异机制尚不清楚。申请项目拟采用13C-CO2连续标记技术，量化典型农田与自然土壤自养微生物碳同化速率及其潜力差异；通过土壤有机质物理-化学分组方法，探讨自养微生物同化碳在土壤碳库不同粒径和不同腐殖质组分中的分配特征，以揭示其对土壤有机碳的贡献与稳定性机理；通过13C–DNA/RNA-SIP为核心的环境基因组学技术和克隆测序技术，构建农田土壤和自然土壤CO2同化的关键功能基因（cbbL、cbbM、coxL、aclB、accA和hcd）文库，同时结合实时荧光定量PCR技术，明确参与CO2同化作用的关键功能微生物群落结构和数量特征，揭示典型农田与自然土壤自养微生物固碳速率及其功能种群差异的分子机理。通过上述研究可加深对微生物介导的土壤碳循环过程以及陆地生态系统碳循环机制的全面的认识。

Autotrophic microbes are widespread in soils. However, the differences in microbial process and mechanisms of microbial autotrophic carbon dioxide fixation in typical agricultural and natural soils remain poorly understood. Therefore, we’ll use typical agricultural and natural soils incubated in microcosms, continuously labeled 13C-CO2 atmosphere to track labeled C incorporation in soil organic matter (13C labeled soil organic carbon) and the acitive carbon pooles (13C labeled microbial biomass and dissolve orangic carbon). The potential CO2 assimilation rates in typical agricultural and natural soils will be assessed. Combining 13C-DNA/RNA-SIP, clone library and real-time PCR techniques, key functional genes including cbbL, cbbM, coxL, aclB, accA and hcd genes will be analysed to investigate the structure, diversity and abundance of autotrophic bacterial communities involved in CO2 fixation, and subsequently to identify the differences in microbial CO2 assimilation mechanisms in typical agricultural and natural soils. This project will provide in-depth understanding of terrestrial ecosystem carbon cycle.