肠道菌群在宿主各种生理和病理过程中起着关键作用。我们之前研究发现，Segmented Filamentous Bacteria (SFB)在小鼠不同阶段先后激活先天性淋巴细胞和T细胞来维持肠道菌群稳定和肠道稳态。然而目前肠道免疫系统如何调控肠道不同菌种之间的稳态平衡尚不清楚。我们未发表数据表明在不同基因型小鼠体内，SFB和Enterobacteriaceae的数量呈负相关关系。本项目将围绕以下几个问题展开深入研究：1. SFB利用宿主免疫系统抑制Enterobacteriaceae的数量；2. Enterobacteriaceae在Il22-/-Rag1-/-小鼠体内对SFB的抑制作用及分子机制；3. SFB和Enterobacteriaceae的竞争关系对于宿主在各种疾病中的影响。本项研究将阐明肠道菌种之间以及和宿主免疫系统的互作机制，为治疗肠道菌群失调引发的疾病提供新的靶点和方法。

Gut microbiota plays critical roles in host physiology and pathology. In our recently published study, we found that Segmented Filamentous Bacteria (SFB) sequentially activated innate lymphoid cells and T cells, and these activities were essential for maintaining the microbiota stability and gut homeostasis. However, whether the gut immune system is involved in or influences the inter-bacterial competition is largely unknown. Interestingly, our data shows that the abundance of SFB and Enterobacteriaceae are inversely correlated in different immuno-deficient mice. Therefore, this project will focus on the following questions: 1. SFB utilizes host immune system to suppress Enterobacteriaceae; 2. Inhibition of SFB by Enterobacteriaceae in Il22-/-Rag1-/- mice and the molecular mechanisms; 3. The impact of this inter-bacterial competition on the host in different disease models. Hopefully, this study will reveal new insights into the relationship among individual bacteria and host immune system, and provide new targets and strategies for the prevention and treatment of disease induced by gut microbiota dysbiosis.