FIG 5.
The region responsible for stimulating switching is encoded toward the 5′ end and upstream of aadB. (A) The insert in plasmid pWHaadB contains part of the 5′ end of the intI ORF (gray rectangle), as well as the promoters for intI (PintI, gray bent arrow) and aadB (Pc, green bent arrow). To determine which part of the insert was responsible for stimulating switching, pWHaadB was mutagenized with EZ-Tn5 <Kan-2>. Insertions that blocked the stimulation of switching are indicated by closed triangles, whereas insertions that did not affect sectoring are indicated by open triangles. Plasmids were then generated containing truncated inserts of different lengths to further test for the stimulation of switching in the LSO variant. The remaining length of each plasmid insert is indicated in parentheses. Plasmids pWHaadB-T (B), pWHaadB-TA (C), pWHaadB-TB (D), and pWHaadB-UP (E) were transformed into the LSO variant, and switching to AV-T was measured for 24-h-old colonies. Data shown represent averages, SEMs, and individual switching frequencies from six colonies collected from at least two independent experiments. ****, P ≤ 0.0001, one-way ANOVA with Tukey’s posttest.