FIG. 7.
Effects of cell density on expression of the pepT-lacZ fusion. (A) The PHL665 strain was grown in M63-mannitol medium in a shaker at 30°C. Samples were taken at intervals for determination of OD600 (open circles) and specific β-galactosidase activity (filled circles). (B) Bacteria were grown in LB medium (open squares) or conditioned LB medium prepared as described in Materials and Methods from a stationary-phase culture of strain DH5α (filled squares). Growth curves in the two media were similar. This experiment is representative of three.