FIG. 2.

Growth-phase-dependent induction of Pu in a P. putida MAD2 derivative lacking ptsN. (A) P. putida MAD2 ptsN::Km cells from a stationary-phase culture were diluted to an A₆₀₀ of ∼0.05 and regrown at 30°C in M9-caa medium with or without glucose as an extra C source as indicated. β-Galactosidase levels were followed soon after growth resumed in the fresh medium. (B) Same as above, but instead with P. putida MAD2 ptsN::Km cells transformed with plasmid pJM154, which harbors a copy of the ptsN gene under the control of a Plac promoter. Note that although Pu lacks inhibition by glucose in the ptsN mutant, it still retains its exponential silencing to the same degree as the wild-type strain. (C) Comparison of the intracellular levels of ς⁵⁴ in P. putida MAD2 and P. putida MAD2 ptsN::Km cells in the different culture conditions described above. The loss of the ptsN gene did not grossly affect ς⁵⁴ amounts as detected by Western blot with anti-ς⁵⁴ polyclonal serum.