Fig. 5.

The effects of spr deletion on the flipping of fimS. A, The invertible element orientation assay uses the asymmetrical digestion site of SnaBI within fimS to determine the orientation of the fim promoter. The 602-bp fimS-plus fragment was PCR amplified with the primers Ch1F and Ch1R. The SnaBI restriction fragments of the phase-ON fimS-plus are 404 bp and 198 bp. The SnaBI restriction fragments of the phase-Off fimS-plus are 160 bp and 442 bp. B, The ratios of the phase-ON bacterial cells of WT-RS218 and Δspr-RS218 statically grown in LB broth, which were determined by the invertible element orientation assay as described under “Experimental Procedures.” C, The representative image results of the invertible element orientation assay of WT-RS218, Δspr-RS218, and Δspr-RS218 trans-complemented with the spr gene. Ten colonies of each strain of the bacteria were randomly selected from the agar plates and then subjected to the invertible element orientation assay. The 198-bp (phase-ON) and 168-bp (phase-OFF) bands are shown in the results. D, The ratios of the phase-ON cell-containing colonies of WT-RS218, Δspr-RS218, and Δspr-RS218 trans-complemented with the spr gene. The results were derived from 5 independent experiments. For each independent experiment, 10 colonies of each strain were selected from the agar plates and then subjected to the invertible element orientation assay. The results are shown as the mean ± S.D.