Effects of AI-2 quorum sensing related luxS gene on Streptococcus suis formatting monosaccharide metabolism-dependent biofilm.

Biofilm is the primary cause of persistent infections caused by Streptococcus suis (S. suis). Metabolism and AI-2 quorum sensing are intricately linked to S. suis biofilm formation. Although the role of the AI-2 quorum sensing luxS gene in S. suis biofilm has been reported, its specific regulatory mechanism remains unclear. This study explored the differences in biofilm formation and monosaccharide metabolism among the wild type (WT), luxS mutant (ΔluxS) and complement strain (CΔluxS), and Galleria mellonella larvae were used to access the effect of luxS gene deletion on the virulence of S. suis in different monosaccharide medias. The results indicated that deletion of the luxS gene further compromised the monosaccharide metabolism of S. suis, impacting its growth in media with fructose, galactose, rhamnose, and mannose as the sole carbon sources. However, no significant impact was observed in media with glucose and N-acetylglucosamine. This deletion also weakened EPS synthesis, thereby diminishing the biofilm formation capacity of S. suis. Additionally, the downregulation of adhesion gene expression due to luxS gene deletion was found to be independent of the monosaccharide medias of S. suis.

Gao S ，Yuan S ，Quan Y ，Jin W ，Shen Y ，Liu B ，Wang Y ，Wang Y ... -  《-》

The LuxS/AI-2 system of Streptococcus suis.

Wang Y ，Wang Y ，Sun L ，Grenier D ，Yi L ... -  《-》

The LuxS/AI-2 Quorum-Sensing System of Streptococcus pneumoniae Is Required to Cause Disease, and to Regulate Virulence- and Metabolism-Related Genes in a Rat Model of Middle Ear Infection.

Yadav MK ，Vidal JE ，Go YY ，Kim SH ，Chae SW ，Song JJ ... -  《Frontiers in Cellular and Infection Microbiology》

Effects of metformin on Streptococcus suis LuxS/AI-2 quorum sensing system and biofilm formation.

Streptococcus suis (S. suis) regulates biofilm formation through LuxS/AI-2 quorum sensing system, increasing drug resistance and exacerbating infection. The anti-hyperglycaemic agent metformin has anti-bacterial and anti-biofilm activities. This study aimed to investigate the anti-biofilm and anti-quorum sensing activity of metformin in S. suis. We first determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of metformin on S. suis. The results indicated that metformin showed no obvious inhibitory or bactericidal effect. Crystal violet staining showed that metformin significantly inhibited the formation of S. suis biofilm at sub-MIC concentration, which was also confirmed by scanning electron microscopy. Then, we quantified the AI-2 signal molecules in S. suis, and the results showed that metformin had a significant inhibitory effect on the production of AI-2 signal in S. suis. Inhibition of enzyme activity and molecular docking experiments showed that metformin has a significant binding activity to LuxS protein. In addition, qRT-PCR results showed that metformin significantly down-regulated the expression of AI-2 synthesis-related genes luxS and pfs, and adhesion-related genes luxS, pfs, gapdh, sly, fbps, and ef. Western blotting also showed that metformin significantly reduced the expression of LuxS protein. Our study suggests that metformin seems to be a suitable candidate for the inhibition of S. suis LuxS/AI-2 QS system and prevention of biofilm formation, which provided a new idea for the prevention and control of S. suis.

Zuo J ，Shen Y ，Wang H ，Gao S ，Yuan S ，Song D ，Wang Y ，Wang Y ... -  《-》

Crystal Structure and Identification of Two Key Amino Acids Involved in AI-2 Production and Biofilm Formation in Streptococcus suis LuxS.

Wang Y ，Yi L ，Wang S ，Fan H ，Ding C ，Mao X ，Lu C ... -  《PLoS One》