FIG. 4.

Levels of expression from the lac promoter of the pSRK vector family can be controlled by inducer concentration. A culture of A. tumefaciens C58 harboring pSRKGm::uidA was grown in MG/L medium to early exponential phase and split into eight equal subcultures. IPTG at the indicated final concentrations was added to seven of the subcultures. The eight cultures were sampled after 4 h (open bars) and 8 h (filled bars) of additional incubation and assayed for β-glucuronidase activity, expressed as modified Miller units, as described in Materials and Methods.