FIG. 3.

Southern hybridization demonstrating that IS150 minicircles and linear IS150 molecules are also generated from wild-type IS150 elements. (A) Design of the probe. Cleavage by BglII divides IS150 into two fragments. The 238-bp probe used should detect the 442-bp right fragment of linear IS150 molecules and a 1,443-bp fragment corresponding to linearized IS150 minicircles. (B) Plasmid DNA from cleared lysate preparations was digested with BglII prior to agarose gel electrophoresis, blotting, and hybridization. A 100-fold excess of plasmid pFDX3922 carrying the wild-type IS150 element (wt) relative to the amount of plasmid pFDX3923 carrying the insA-insB-negative element (insA⁻) was used (based on the amount of supercoiled and nicked circular plasmid DNA as described in Materials and Methods). The positions of marker bands (in base pairs) are indicated on the right. The strain used for transformation was R2136.