Impediment to replication fork movement in the terminus region of the Bacillus subtilis chromosome

Abstract The terminus regions of the chromosomes of three strains of Bacillus subtilis 168 were radioactively labelled by supplying [ 3 H]thymine towards the end of a round of replication. These strains lacked or contained the prophage SP βc 2. Following restriction endonuclease digestion of the purified DNA and fluorography, an SPβ c 2-related perturbation of the terminus-labelling profile was observed, which was completely consistent with the previously suggested existence of an impediment to replication fork movement ( terC ) within a Bam HI 24.8 × 10 3 base fragment (Weiss & Wake, 1983). The present data suggest that terC is located within the 11.4 × 10 3 base Bam HI + Sal I double-digest portion of this Bam HI fragment.