土壤中的根际促生菌在促进植物生长或降低植物病害方面发挥着积极的作用，它对改良土壤养分利用率和提高作物产量有着重要意义。这种相互作用的介导过程是通过小分子信号调控完成的，其中群体感应（QS）信号分子发挥着重要作用。群体感应本是细菌种群内的交流方式，近几年发现它在微生物种群间的互作与代谢调控中具有关键作用。然而根际促生菌的QS信号对促生作用的调控机理还是一个有待进一步揭示的科学问题。本申请拟选取土壤中代表性的根际促生菌（嗜根寡养单胞菌），生物信息学分析表明其具有可扩散性信号分子（diffusible signal factor, DSF）QS系统同源基因，利用系统生物学及微生物生态学方法，来回答以下科学问题：嗜根寡养单胞菌的DSF QS调控系统是否是促进植物生长的关键因素？其QS调控系统如何影响植物根际微生物的种群关系和功能？这些问题的揭示将提升对根际促生菌在土壤中生存方式及发挥功效的认识。

Plant growth-promoting rhizobacteria (PGPR) are a group of free-living bacteria that benefit the plant growth and play a major role in the biocontrol of plant pathogens. It is important not only for nutrient-use efficiency in soil, but also for the crop yield and quality. In the rhizosphere, an extensive communication takes place between plants and root-associated microorganisms, involving diversity of released compounds and signals. These chemical signals play important roles in determining the assembly and functioning of rhizosphere communities. Various PGPR have been found to produce quorum sensing (QS) signals, which are known as cell-density-dependent phenomenon mediated by cell-to-cell communication. The identification of QS signals involved in the interaction of PGPR with each others, and the metabolic regulation of soil microorganism, are discovered recently. However, in the soil ecosystem, the mechanism and processes of growth-promoting regulated by QS in PGPR remain poorly understood. The representative PGPR strain of Stenotrophomonas rhizophila, with homologous components to diffusible signal factor (DSF) QS system, is selected in this project. Based on the methods of systems biology and microbial ecology, this project is designed to answer the following scientific questions: 1) whether DSF QS system in S. rhizophila has effects on the key functions of plant growth-promoting; 2) to discuss the mechanisms of control and regulation of the PGPR community structure and function by DSF QS system in S. rhizophila. This project will enhance understanding of the survival process and ecological function of PGPR in soil.