FIG 4.

Depletion of PBP2, but not of the remaining CW synthesis enzymes, leads to VraTSR activation. S. aureus mutants lacking different CW synthesis enzymes, PBP2 (ΔpbpB), PBP3 (ΔpbpC), PBP4 (ΔpbpD), PBP2A (ΔmecA), MGT (Δmgt), or SgtA (ΔsgtA), or encoding a transpeptidase mutant of the essential PBP1 (PBP1TP*) and expressing GFP under the control of the vraTSR promoter, were analyzed by FACS. Only the cells lacking PBP2 (ΔpbpB) showed strong VraTSR activation, while the Δmgt mutant showed low activation levels. Control experiments, where COL Pvra-sGFP cells were grown in the absence (wt) or presence of bacitracin (wt + bacitracin), which induces the VraTSR response, were performed as negative and positive controls, respectively. N = 5,000 cells for each replicate; experiments were done in triplicate. Each point represents the median of one FACS experiment.