FIG. 4.

Confirmation of the residence of two complete toxin operons within the double lysogen genome. (I) Genetic maps showing the location of relevant restriction endonuclease sites and areas recognized by the relevant probes: aph3 ( ), cat (□), Q (▪), and substxB₂ (▧). The asterisk (✽) indicates the position of a PstI site that was lost after a single nucleotide substitution, as confirmed by DNA sequencing. (II) Tabulated data of the RFLP lengths of the relevant AflIII and EcoRI fragments from each isogenic recombinant phage. Fragment sizes are listed in consecutive order beginning at the 5′ end of the maps in part I. (III) Southern blots with probes specific to aph3 (A), cat (B), Q (C), and substxB₂ (D). Lanes 1, 3, and 5 on blots A to D contain EcoRI-digested DNA, and lanes 2, 4, and 6 contain AflIII-digested DNA. The sources of the DNA are E. coli MC1061 lysogens containing the following prophages: lanes 1 and 2, φ24_B::Kan; lanes 3 and 4, φ24_B::Cat; lanes 5 and 6, φ24_B::Kan and φ24_B::Cat.