In addition, we are the first to demonstrate the regulator for vraDE together with bceAB, although

vraDE has already been reported to be related to bacitracin susceptibility (Pietiäinen et al., 2009). BceRS inactivation resulted in the failure of upregulation for vraDE expression by bacitracin, indicating that BceRS regulates two genes, bceAB and vraDE. The expression of two transporters was induced rapidly from 5 min after addition of bacitracin. However, the increased expression was suppressed from 15 min after the addition of a low concentration of bacitracin, speculating that the amount of two transporters by short-time induction was sufficient to resist to low concentration of bacitracin. Also, the inactivation of bceAB, but not vraDE, reduced the oxacillin resistance slightly, suggesting that bceAB may affect the cell wall biosynthesis. Inactivation click here of another transporter, vraFG (MW0623-0624), showing homology with bceAB in B. subtilis, did not cause an Selumetinib concentration alteration in susceptibility to bacitracin. The gene related to this transporter, vraFG, is located downstream of apsRS/graRS (MW0621-0622), one of the TCSs in S. aureus, and this TCS has been demonstrated to regulate vraFG expression (Li et al., 2007). Also, vraFG was reported to be associated with vancomycin susceptibility (Meehl et al., 2007). In this study, we also had a similar result

that vraFG

mutation led to increase the susceptibility to vancomycin (Table 3). We determined that apsRS inactivation did not affect the increased expression of vraDE and bceAB by bacitracin induction (data not shown), so we concluded that apsRS and vraFG were not associated with bacitracin susceptibility in S. aureus. Furthermore, it was reported that bacitracin induced the expression of vraSR (Kuroda et al., 2003), implying the possibility of the relation of BceRS with VraSR. However, we found the vraSR about expression was increased by bacitracin in bceRS mutant (data not shown). Also, in vraSR mutant, the expression of bceA and vraD was significantly induced by bacitracin. These results indicate that BceRS has no effect on VraSR expression by bacitracin. Previously, the bacA gene (MW0645) affecting bacitracin susceptibility was reported in S. aureus (Chalker et al., 2000). The gene bacA was first identified on a multicopy plasmid in E. coli, causing an increase in isoprenol kinase activity and decrease in bacitracin susceptibility. Therefore, BacA in S. aureus is considered to have an undecaprenol kinase activity related to undecaprenol pyrophosphate recycling. Inactivation of bacA resulted in an increase in the susceptibility to bacitracin, showing an MIC of 4 μg mL−1 in the bacA mutant compared with 64 μg mL−1 in the wild type (RN4220) (Chalker et al., 2000).