A new two-component regulatory system involved in adhesion autolysis, and extracellular proteolytic activity of Staphylococcus aureus

A transposition mutant of Staphylococcus aureus was selected from the paren t strain MT23142, a derivative of strain 8325. The site of transposition wa s near the 5' terminus of the gene arlS. ArlS exhibits strong similarities with histidine protein kinases. Sequence analysis suggested that arlS forms an operon with upstream gene arlR. The predicted product of arlR is a memb er of the OmpR-PhoB family of response regulators. The arlS mutant formed a biofilm on a polystyrene surface unlike the parent strain and the compleme nted mutant. Biofilm formation was associated with increased primary adhere nce to polystyrene, whereas cellular adhesion was only slightly decreased. In addition, the arlS mutant exhibited increased autolysis and altered pept idoglycan hydrolase activity compared to the parental strain and to the com plemented mutant. As it has been shown for coagulase-negative staphylococci that some autolysins are able to bind polymer surfaces, these data suggest that the two-component regulatory system ArlS-ArlR may control attachment to polymer surfaces by affecting secreted peptidoglycan hydrolase activity. Finally, the arlS mutant showed a dramatic decrease of extracellular prote olytic activity, including serine protease activity, in comparison to the w ild-type strain and the complemented mutant, and cells grown in the presenc e of phenylmethylsulfonyl fluoride (a serine protease inhibitor) showed an increased autolysin activity. Since the locus arlR-arlS strikingly modifies extracellular proteolytic activity, this locus might also be involved in t he virulence of S. aureus.