FIG. 8.

DNA replication at oriP of B95-8-derived strains B-531, which contains wild-type oriP, and B-ΔDS-8, which lacks the DS. The results of 2D gel analysis are shown for each (left), along with a diagram summarizing the gel patterns generated by different replication intermediates (right). (A) For B-531, a 3.5-kb EcoRI-DraI segment was analyzed as performed for P3-531 (Fig. 6). With oriP intact, the same replication intermediates as those shown in Fig. 6 were observed, but note the increased initiation activity at oriP, indicated by the higher ratio of intensity of the bubble arc (b) to the Y arc (a). (B) For B-ΔDS-8, a 4.8-kb SacI segment was analyzed. Initiation was not detected. Spots 2 and 3, reflecting pausing at the FR by forks moving in each direction, were shifted to higher positions on the Y arc because the FR is closer to the center of the SacI fragment.