FIG. 1.
Transcriptional regulation of parEp in synchronous swarmer and stalked cell cultures. (A) Transcriptional activity of a parEp-lacZ fusion (PC4828) during the C. crescentus swarmer cell cycle as assayed by radioimmune precipitation of β-galactosidase. Division occurred at 150 min. (B) Transcriptional activity of a parEp-lacZ fusion (PC4828) during the C. crescentus stalked cell cycle as assayed by radioimmune precipitation of β-galactosidase. Division occurred at 120 min. Activity is plotted as a percentage of maximal expression. Note that 1.0 division unit for the stalked cell cycle corresponds approximately to the period of 0.4 to 1.0 division unit of the swarmer cell cycle. Expression of pulse-labeled FlgE protein served as an internal control for these synchrony experiments and those shown in Fig. 2. The times of swarmer to stalked cell differentiation and completion of cell division (1.0 division unit) are indicated at the bottoms of panels A and B along with the corresponding G1, S, and G2 phases.