Results of in vivo fork-arrest assays in B. subtilis strains producing wild-type RTP or RTP.E30K. (A) Plasmid fork-arrest assays. Lanes 1 and 3 are negative controls for strains SU342 (RTP) and SU369 (RTP.E30K), respectively, harboring pWS64-1 which lacks TerI. Lanes 2 and 4 show strains SU342 and SU369, respectively, harboring the TerI-containing pWS66-1. The four cultures were grown in the presence of 1 mM IPTG. (B) TerIII chromosomal fork-arrest assays. Lane 1 is a negative control for chromosomal DNA from an isogenic strain, SU341, lacking the rtp gene. Lanes 2 and 3 show SU342 and SU369 chromosomal DNA. The DNA was isolated from cultures grown in Penassay broth–1 mM IPTG. The bands corresponding to the fork (f), linear (l), and arm (a) species are indicated.