FIG 1.
Expression of sigP is specifically induced by β-lactams. All the strains contained PsigP-lacZ in either a wild-type (THE2549), a ΔsigP-rsiP (EBT232), or a Δbla1 (EBT215) background. Mid-log cells were washed and diluted 1:100 in molten LB agar containing X-Gal (100 μg/ml) and poured into empty 100-mm petri dishes. Filter disks containing cefoxitin (Cef) (1 μl of 5-mg/ml cefoxitin), bacitracin (Bac) (1 μl of 50-mg/ml bacitracin), nisin (Nis) (3 μl of 100-mg/ml nisin), vancomycin (Van) (1 μl of 10-mg/ml vancomycin), cefmetazole (Cmet) (1 μl of 5-mg/ml cefmetazole), polymyxin B (Poly) (1 μl of 50-mg/ml polymyxin B), kanamycin (Kan) (1 μl of 10-mg/ml kanamycin), piperacillin (Pip) (1 μl of 5-mg/ml piperacillin), cephalothin (Cthin) (1 μl of 50-mg/ml cephalothin), ramoplanin (Ram) (1 μl of 25-mg/ml ramoplanin), cefoperazone (Cper) (1 μl of 50 mg/ml cefoperazone), phosphomycin (Phos) (1 μl of 100-mg/ml phosphomycin), Amp (2 μl of 200-mg/ml ampicillin), cephalexin (Clex) (1 μl of 50-mg/ml cephalexin), Erm (1 μl of 5-mg/ml erythromycin), and methicillin (Meth) (2 μl of 100-mg/ml methicillin) were then placed on the top agar and incubated for 16 h at 30°C.