Regulation of lysP expression by lysine, arginine, and ArgP. (A) Effect of the argP deletion on lysP expression. Parent strain MG-LR (PlysP::lacZ ΔlysP) and the argP mutant MG-LR17 (PlysP::lacZ ΔargP::Camr ΔlysP) were grown aerobically in glucose minimal medium with or without the addition of 0.1 mM lysine. When cultures reached an OD600 of ∼0.8, samples were analyzed for β-galactosidase activity. (B) Complementation of the argP mutant with pBADargP. Strains MG-LR/pBAD24 (○, •), MG-LR17/pBAD24 (▵, ▾), and MG-LR17/pBADargP (□, ▪) were grown in glucose minimal medium without lysine (open symbols) or with the addition of 0.1 mM lysine (closed symbols). Arabinose at a final concentration of 0.2% (wt/vol) was added to all cultures after 2.5 h of growth. β-Galactosidase activities were determined at different time points during growth. (C) Effect of basic amino acids on lysP expression. Strains MG-LR and MG-LR17 were cultivated as described for panel A in glucose minimal medium without supplementation or supplemented with 10 mM lysine (lys.) and/or arginine (arg.) for determination of β-galactosidase activity. All experiments were performed at least three times, and where indicated, error bars represent standard deviations from the means.