Role of the maltose-utilizing (MAL) gene cluster in capsule expression and virulence of Streptococcus suis

Streptococcus suis (SS) is an important pathogen that poses a great threat to animal and human health. In this study, key phosphorylation sites of VraSRSS were identified and a MAL gene cluster of SS was identified by transcriptomic analysis. The role of the MAL gene cluster in SS virulence was examined through animal infections and cell experiments, with further investigations using transmission electron microscopy revealing its participation in capsule synthesis. Furthermore, it was confirmed that transcriptional regulator MalR negatively regulates the expression of the MAL gene cluster while identifying binding sites for MalR protein. Overall, regulation by VraSRSS influences the activity of the MAL gene cluster which contributes to SS's pathogenic process as an essential virulence factor. It also controls capsule synthesis to enhance both adaptability and virulence.