Catabolite control protein a of Streptococcus suis type 2 contributes to sugar metabolism and virulence

Catabolite control protein A (CcpA) is the major transcriptional regulator in carbon catabolite repression in several Gram-positive bacteria. We attempted to characterize the role of a CcpA homologue of Streptococcus suis type 2 in sugar metabolism and virulence. Addition of glucose or sucrose to the defined medium significantly reduced the activity of raffinose-inducible alpha-galactosidase, cellobiose-inducible beta-glucosidase, and maltose-inducible alpha-glucosidase of the wild-type strain by about 9, 4, and 2-3 fold, respectively. Deletion of ccpA substantially derepressed the effects of repressing sugars on alpha-galactosidase or beta-glucosidase activity. The ccpA deletion mutant showed reduced expression of virulence genes sly and eno (P < 0.05), decreased adhesion to and invasion into endothelial cells (P < 0.05), and attenuated virulence to mice with significant reduction of death rate and bacterial burden in organs, as compared to the wild-type strain. Both the in vitro and in vivo defect phenotypes were reversible by ccpA complementation. Thus, this study shows that CcpA of S. suis type 2 plays an important role in carbon catabolite repression and virulence.