Detection of Autoinducer-2 and Analysis of the Profile of luxS and pfs Transcription in Streptococcus suis Serotype 2

The only quorum sensing (QS) system shared by Gram-positive and Gram-negative bacteria involves the production of autoinducer-2 (AI-2). However, there have been no reports concerning the AI-2 in Streptococcus suis serotype 2 (SS2). In this study, we investigated AI-2 production and analyzed the relationship between the transcription level of luxS and pfs and AI-2 production. A homologue of luxS, the gene required for AI-2 synthesis in Vibrio harveyi, was isolated from the SS2 genome. V. harveyi BB170 bioassay demonstrated luxS functionality in SS2 and its ability to complement the luxS-negative phenotype of Escherichia coli DH5 alpha. Further studies showed that AI-2 activity peaked in the late exponential phase, and sodium chloride or glucose increased the production of AI-2. Real-time PCR showed that the level of transcription of pfs is highly correlated with the level of AI-2 production, while the level of transcription of luxS does not correlate with the level of AI-2 production. The results presented here demonstrate that SS2 can secrete AI-2 and that the profile of pfs transcription is highly correlated with the level of AI-2 production.