FIG. 4.

Effect of 3-MBA on spoIID-lacZ expression. UOT1285 carrying plasmid pKZIID-1 (29) was grown in 2× SG medium containing 0.1% glucose and 5 μg of kanamycin per ml at 37°C. At the times indicated by the arrows, 3-MBA was added to the medium as described in the legend to Fig. 3. (A) Growth measured by the OD₆₆₀. (B) Expression of spoIID-lacZ-directed β-galactosidase activity. Since most of cells eventually lysed (decreasing the OD₆₆₀ values) when 3-MBA was added before T₂, few developing cells were present after cell lysis occurred. Hence, 1 U of the β-galactosidase activity in the medium was expressed as the A₄₂₀ per milliliter per minute × 1,000 (A₄₂₀ is absorbance at 420 nm). Aliquots of 0.2 ml were withdrawn from the medium at the various times, mixed with 0.3 ml of 5/3× Z buffer, and treated with a few drops of toluene. Subsequent steps for assay of the β-galactosidase activity were carried out as described previously (15). Closed circles in both panels indicate the controls (for which no drug was added).