Figure 7.

Effects of BglG levels on residual bgl operon transcriptional activities in cells before plating and after plating onto M9 + salicin agar plates. The wild-type, Iq-G and Ptet-G cells (all carrying the operon lacZ reporter, Pbgl-bglG-lacZ, chromosomally integrated at the lacZ site) were cultured in LB for 8 h, washed 2x with M9 salts and diluted to OD₆₀₀ of 0.1 before plating. The operon activities before plating, as indicated by β-galactosidase activities, were measured, based on the operon lacZ reporter. An amount of 200 μL of the cell suspensions were applied onto M9 + salicin agar plates that were incubated at 30 °C. After 1.5 days of incubation, the cells were washed off the plates using an M9 salts solution, and the cell suspensions were assayed for β-galactosidase activities (i.e., operon activity after plating) (see Methods). β-galactosidase activities were measured following expression of bglG under the control of the native bgl operon promoter, or after overexpression of bglG using either the lacIq promoter or the stronger Ptet promoter. Measurements were made either before plating (left) or after plating (right) as indicated.