Rot and Agr system modulate fibrinogen-binding ability mainly by regulating clfB expression in Staphylococcus aureus NCTC8325.

Staphylococcus aureus is an important human pathogen that causes a variety of diseases, ranging from localized skin infections to life-threatening systemic infections. The success of S. aureus as a pathogen is partly due to its ability to adhere to a wide range of host tissues by binding to host extracellular matrix proteins such as fibrinogen, fibronectin, and collagen. Staphylococcus aureus expresses two proteins that can bind specifically to fibrinogen, clumping factors A and B (ClfA and ClfB). Repressor of toxins (Rot) is known to be a global regulator of virulence gene expression in S. aureus. The translation of Rot is regulated by the staphylococcal accessory gene regulator (Agr) quorum-sensing system. In this study, we demonstrated that Rot and the Agr system in S. aureus NCTC8325 can affect the bacterial binding ability to human fibrinogen (Fg) under different bacterial growth phases. Our real-time RT-PCR results indicated that both Rot and the Agr system have no significant effect on clfA expression. However, Rot is an activator of clfB, and Agr/RNAIII can regulate clfB expression via Rot. Gel shift data further suggested that Rot might regulate clfB expression by directly binding to the promoter region of clfB. Moreover, Rot and the Agr system exhibited consistent regulatory effects on clfB transcription and bacterial Fg-binding ability, suggesting that Rot and the Agr system might affect bacterial Fg-binding ability mainly through regulating clfB transcription.