群体感应对土壤好氧反硝化细菌（脱氮副球菌）的调控机制

土壤的反硝化作用是氮元素生物地球化学循环的重要环节，不仅决定着土壤氮素的利用程度，还与硝酸盐淋失和氧化亚氮的释放等生态环境问题相关。微生物介导的反硝化过程通常被认为是在厌氧条件下进行的，但在土壤生态系统中同时存在好氧反硝化作用。虽然经过几十年的研究，对好氧反硝化的电子传递系统已有一定的认识，但是对实际土壤环境中好氧反硝化菌的分子调控机制并没有明确的答案。本项目结合前期开展的一些工作，以脱氮副球菌为反硝化模式菌，从群体感应（quorum sensing, QS）角度出发，回答反硝化微生物的QS系统是否对其生长代谢产生全局调控？不同生存状态下QS调控作用的差异？QS系统是否对其本身的关键功能产生调控？QS如何影响反硝化过程等科学问题。这一课题的完成有助于理解好氧反硝化细菌在土壤生态系统中的个体生态行为，同时为土壤氮循环中微生物的代谢调控提供一些基础理论认识。

Denitrification is a major branch of the biogeochemical nitrogen cycle in soil. It is a major process of loss of fertilizer nitrogen resulting in decreased efficiency of fertilizer use, and an important process, contributing nitrous oxide to the atmosphere. Reactions of denitrification occur in many microbes under anaerobic condition. However, it is noteworthy that biological reduction of nitrate under aerobic conditions was reported. The mechanisms of bacterial aerobic denitrification were investigated electronically in Paracoccus denitrificans, typical bacteria of aerobic denitrification research, but the physiological function and metabolic regulation mechanism of P. denitrificans in the soil ecosystem remain poorly understood. With the knowledge reserve of quorum sensing, a form of cell-cell communication that regulates gene expression, we could answer the following scientific questions: 1) whether global regulation is driven by QS system in P. denitrificans; 2) to discuss the QS regulation mechanism of P. denitrificans in different living conditions; 3) whether these QS signals have effects on the key functions of P. denitrificans; 4) to discuss the mechanism of control and regulation of the denitrification process by QS. This project will provide clues for understanding the individual-based bacterial ecological behavior of this aerobic denitrifier. Meanwhile, the study is expected to lay a solid foundation for further research of microbial regulation in soil nitrogen circulation.