FIG. 8.

SEM micrographs of MR/P ON and MR/P OFF cells colonizing the murine bladder. Mice were transurethrally inoculated with 10⁸ CFU of the mutants in independent experiments. At 4 days postinoculation, the ureters of infected mice were ligated with surgical thread, and the bladders were infused through the urethra with fixative (2% glutaraldehyde, 2% formaldehyde). After the urethras were tied off, the bladders were aseptically removed and processed for SEM as described in Materials and Methods. MR/P ON colonized the bladder uroepithelium (A and B), while MR/P OFF colonized the lamina propria where bladder cells had sloughed off (C [arrows point to MR/P OFF] and D). Bars = 10 μm (A), 2 μm (B and D), and 15 μm (C).