Expression of pep genes in B. cereus ATCC 14579 and B. cereus ATCC 14579 Δ plcR. Expression of Ppep1'-Z (circle), Ppep2'-Z (square), and Ppep3'-Z (triangle) in wild-type (closed symbols) and B. cereus Δ plcR (open symbols) strains. Grey symbols, OD600 of cultures of bacteria. Cells were grown at 37°C in LB medium. Time zero indicates entry into stationary phase. Standard deviations of triplicate measurements are shown for β-galactosidase activity.