低核酸含量（LNA）细菌在水环境中广泛存在，并在生态系统中具有重要的作用。目前大部分关于LNA菌的研究都是在海洋环境中展开，淡水环境中LNA细菌的研究非常有限。本项目将围绕在淡水环境中LNA群落动态与代谢机制展开研究。以LNA菌群为研究对象，分析其不同淡水环境中的分布及群落结构，分离培养LNA代表性菌株。分析流域尺度上LNA菌群的时空变化及群落组成，提出并阐明淡水环境中LNA菌群时空地理动态变化规律。分析LNA菌对不同碳源的代谢能力及途径，通过生物信息学分析，揭示LNA细菌的保守基因。阐明LNA细菌对不同环境压力的响应机理。本项目的研究成果将促进对微生物群落动态整体认识，有助于进一步全面掌握LNA菌的分布及代谢机制，并为微生物资源的进一步开发和利用奠定基础。

Most planktonic bacteria are “uncultivable” with conventional methods, and flow cytometry (FCM) is one of the methods that have been applied to study these bacteria. In natural aquatic environments, bacteria with high (HNA) and low (LNA) nucleic acid content are commonly observed with FCM after staining with fluorescent dyes. LNA bacteria contribute to at least half of the numbers in microbial community and are reported to have important ecological functions. To date, most studies have focused on the LNA bacteria in marine environments. Knowledge of freshwater LNA bacteria is very limited. The present project set out to investigate the community dynamics and ecological functions of LNA bacteria in freshwater environments. We aim to analyze the distribution of LNA bacteria in various freshwater environments and isolate novel and representative LNA bacterial strains. We’ll also elucidate the temporal and spatial distribution of LNA bacterial community along Haihe River and Tuanbo Lake. We’ll analyze the growth kinetics of LNA bacteria under various nutrient conditions. Furthermore, we aim to illustrate the response of LNA bacteria to various environmental pressure. The results of the project would provide 1) new insights towards LNA bacterial distribution and ecological functions, 2) foundation for microbial resource discover and management.