The ClpX chaperone controls autolytic splitting of Staphylococcus aureus daughter cells, but is bypassed by β-lactam antibiotics or inhibitors of WTA biosynthesis
Fig 7
β-lactam antibiotics targeting PBP1or BPB3, and WTA (TarO) inhibitors specifically promote growth of the clpX mutant.
(A) The S. aureus wild-type strains, SA564 (MSSA) and USA300 JE2 (MRSA) and the clpX deletion strains derived here from were grown exponentially in TSB at 37°C. At OD600 = 0.5, cultures were diluted 101, 102, 103 and 104-fold, and 10 μl of each dilution was spotted on TSA plates in the presence or absence of subinhibitory concentrations (1/5 MIC of wild-type) of β-lactams with different PBP specificities as indicated; the TarO inhibitors tunicamycin (0.5 ug/ml), and tarocin A1 (0.5 ug/ml), or the TarG inhibitor, targocil (0.2 ug/ml), and incubated at 30°C for 24 h. (B) S. aureus SA564 wild type and the clpX deletion strains were grown overnight at 37°C, diluted 1:200 and grown at 37°C until mid-exponential phase. These cultures were then diluted into TSB alone (control) or containing increasing concentrations of tunicamycin, tarocin A or targocil in a 96-well format, and the plates were incubated for 24 h at 30°C. The average final OD and standard deviations from three biological replicates were plotted. (C) The S. aureus SA564 wild-type strain, and the indicated mutant strains were grown exponentially in TSB at 37°C. At OD600 = 0.5, cultures were diluted 101, 102, 103 and 104-fold, and 10 μl of each dilution was spotted on TSA plates and incubated at 30°C for 24 h.