Fig. 5.

Blocking one replisome does not inhibit the other. Strain AB2937, containing an ectopic ter site at the lacZ locus, 28 map minutes right of the replication origin (Inset), was synchronized and induced to express Tus protein. Samples were taken 20 (green), 40 (blue), and 70 (purple) min after initiation. Shown are abundance versus distance from oriC for the rightward, blocked and leftward, unblocked halves of the chromosome, respectively. oriC is at the left edge, and the natural terminus is at the right edge. Black vertical lines mark the position of the ectopic ter in A and the equivalent position in B. At 20 min, the rightward fork had reached the ectopic ter, but at 40 min, the fork had stalled there. A subpopulation that bypassed the ter was visible at 30–50 min as a slight slope. Meanwhile, the entire population of leftward forks proceeded normally, unaffected by the blocking of the rightward fork.