Figure 2.

Regulated synthesis of Lon. (A) Increasing levels of Lon produced with increasing arabinose concentrations. LVM781 (Δlon)/pBADlon⁺ and LVM783 (lon⁺)/pBAD24 were grown in LB at 32°C to an OD₆₀₀ of 0.2. Cultures were split, and arabinose was added at the final concentration indicated at the top of the panel. After 2 hr of induction, 1 ml of culture was removed and TCA-precipitated. Proteins were separated by SDS/PAGE, and Lon was detected by Western blot, as described in Materials and Methods. (B) Arrest of growth caused by Lon overproduction in minimal medium. Strains were grown at 32°C in minimal medium (M63) supplemented with glycerol (0.2%), vitamin B1 (0.0001%), and casamino acids (0.1%), containing arabinose as indicated below. The graph represents OD₆₀₀ as a function of time. Strains used were: LVM781 (Δlon)/pBADlon⁺ grown in the presence of 0.001% (○), 0.01% (◊), or 0.1% (▵) arabinose; LVM781/pBAD24 with 0.1% arabinose (●); and LVM783 (lon⁺)/pBAD24 with 0.1% arabinose (■).