Regulation of saeRS, agrA and sarA on sasX Expression in Staphylococcus aureus

Background: The spread of Staphylococcus aureus and the types of infection caused by S. aureus are closely related to the secretion of a variety of adhesion proteins, which could be controlled by a variety of regulatory systems. However, for the newly discovered adhesion protein SasX, the regulatory mechanism is not completely clear. Objectives: The current study aimed at investigating the regulation of Staphylococcal accessory gene regulator A (agrA), Staphylococcal accessory regulator A (sarA), and two-component signal transduction system (saeRS) on the adhesion protein SasX. Methods: In this research, a saeRS mutant strain, a sarA mutant strain, and a agrA mutant strain were constructed by allelic replacement. In this study mRNA and protein expression levels of sasX in wild-type HS770 and knockout strains were studied to investigate the effects of regulatory factor saeRS, agrA, and sarA on adhesion protein SasX. Results: In contrast with the wild strain HS770, the transcriptional expression of sasX was highest at on the sixth hour time point in HS770ΔagrA and at nine and twelve hours in HS770ΔsarA. However, the sasX transcription level in HS770ΔsaeRS mutant strains had little change at different time points. Western-blot results suggested that the sasX expression level of wild strains was the highest at 6 hours; HS770ΔsaeRS mutation strains had no expression peak at 6 hours. The expression level of HS770ΔagrA mutant strains decreased at 6 hours of expression, however, increased at 9 hours and 12 hours; the expression level of HS770ΔsarA mutation knockout increased at three, six, nine, and twelve hours. Conclusions: All the results showed that agrA and sarA have negative regulation on sasX, but saeRS may not regulate sasX.