粪肠球菌是难治性根尖周炎的主要致病菌之一，临床上往往综合现有的物理化学手段都难以彻底清除根管深部的细菌，学者们认为这些细菌能够在高碱、寡营养、低氧等特殊环境下长期“潜伏”，进一步研究发现，高碱和寡营养环境下，粪肠球菌的数百个基因表达有显著差异，我们前期的研究也发现在低氧环境中有类似的情况。那么作为兼性厌氧菌的粪肠球菌如何能在低氧环境下形成生物膜，有哪些可能的分子机制，目前尚不清楚。本课题拟在前期利用高通量测序筛选获得的耐低氧粪肠球菌生物膜形成相关基因的基础上，进一步明确dnaK基因及其调控的蛋白在耐低氧粪肠球菌生物膜形成过程中所起的作用以及相关的分子调控网络，为特殊环境下粪肠球菌生物膜形成的调控机制和功能研究提供实验基础和新的思路，并为研发新型抗细菌生物膜药物和抑制剂寻找新的靶点和途径。

Enterococcus faecalis (E. faecalis) is one of the main pathogenic bacteria for refractory periapical periodontitis. It is almost impossible for currently used chemo-mechanical techniques to eliminate the E. faecalis within infected root canals. It is well-accepted that E. faecalis can withstand the harsh environments such as a limited nutrition and a high pH value in endodontically treated canals. Further investigations found that the expression of hundreds of genes significantly changed when the E. faecalis located in a nutrition-limited or/and a high pH value environment (s). Similar changes in gene expression was also noted in our previous study, in which the E. faecalis was cultured under a low-oxygen-contented condition. How did the E. faecalis form biofilm in a low-oxygen-contented environment, and what’s the possibly related molecular mechanism? This is still a unsolved question. Basing on the preliminary data of our previous study, in which biofilm formation related gene of the low-oxygen-resistant E. faecalis isolate was selected using the high-throughput sequencing technique, the purpose of present project is to further illuminate the function and the related molecular mechanism of dnaK gene and its targeted proteins in the biofilm formation of the low-oxygen-resistant E. faecalis isolate.The findings in this research will provide both experimental evidence and new approaches for further investigation in the function and regulatory mechanism of biofilm formation of E. faecalis under specific living environments, and will provide us new targets or methods to develop novel anti-biofilm bactericidal and inhibitory agents.