Fig. 8.
Effect of lrp deletion on lysP expression. E. coli strains MG-LR (PlysP::lacZ, ΔlysP) and MG-LR15 (PlysP::lacZ, ΔlysP, Δlrp::Kmr) were grown aerobically in glucose minimal medium with or without the addition of 0.1 mM lysine (A). To test the effect of leucine on lysP expression, the growth medium was supplemented with 0.6 mM valine and 0.4 mM isoleucine, with or without the addition of 10 mM leucine (B). At different times during growth samples were analyzed for β-galactosidase activity. (C) Complementation of the MG-LR15 (PlysP::lacZ, ΔlysP, Δlrp::Kmr) mutant with the pBADlrp plasmid. Strains MG-LR/pBAD24, MG-LR15/pBAD24 and MG-LR15/pBADlrp were grown in glucose minimal medium, and after 2.5 h 0.2% arabinose (wt/vol) was added to induce the expression of the lrp gene cloned in pBAD24. β-Galactosidase activities were determined in samples collected at different times, before and after induction. All experiments were performed in triplicates and mean values are presented. The standard deviations from the mean were less than 10%.