Abstract: Enterococcus faecium 8-3, which was isolated from koumiss and screened for autoinducer-2 (AI-2), was used to study the effects of growth conditions (pH value, temperature, osmotic pressure, and nutrient condition) on the LuxS/AI-2 quorum sensing system. The production of AI-2 was detected by a biological method and the expression levels of luxS and pfs genes were detected by real-time quantitative PCR. The results showed that mild acid stress induced E. faecium 8-3 to produce the AI-2. Under alkaline conditions, the cell grew better, and the cell density mainly induced the production of AI-2. Under osmotic and low temperature stresses, the growth of E. faecium 8-3 and the production of AI-2 were both inhibited. Cell density controlled AI-2 production. Low nutrient stress could induce E. faecium 8-3 to produce AI-2. The expression of luxS and pfs genes in E. faecium 8-3 under different environmental stresses varied to different degrees, indicating that the LuxS/AI-2 quorum sensing system mediates stress resistance in E. faecium 8-3.

Key words: quorum sensing, autoinducer-2, environmental stress, gene expression