FIG. 4.
fliGHI mutant cannot efficiently reach the cecal epithelium. Three mice were inoculated with 10% bicarbonate prior to infection for 24 h with 5 × 107 CFU of M913(pM979) plus 5 × 107 CFU of SL1344(pDsRed), 5 × 107 CFU of SL1344(pM979) plus 5 × 107 CFU of M913(pDsRed), 5 × 107 CFU of SL1344(pM979) plus 5 × 107 CFU of SL1344(pDsRed), 5 × 107 CFU of SL1344(pM979), or 5 × 107 CFU of SL1344(pM968). Cecal tissue sections were stained with DAPI (grey), Alexa-647-phalloidin (blue), a rabbit anti-LPS antibody, and a goat anti-rabbit serum-rhodamine conjugate (red) (see Materials and Methods). Samples of cecal contents from two mice per group were plated to determine the fraction of pM979 or pM968 carrying bacteria (see Materials and Methods) (panel D, grey columns). (A) Cecum section from a mouse infected with M913(pM979) plus SL1344(pDsRed). (B) Cecum section from a mouse infected with SL1344(pM979) plus M913(pDsRed). (C) Strategy for quantification of GFP-positive red Salmonella cells (green circles) and red Salmonella cells (red circles) within 20 μm (dotted line) of the cecal epithelium (blue). (D) Presence of GFP-positive red Salmonella cells within 20 μm of the cecal epithelium (dotted line) as determined by fluorescence microscopy (black bars; average) (scale on the left side). The fraction of serovar Typhiumurium cells carrying pM979 or pM968 in the cecal contents was determined by replica plating (grey bars; average) (scale on the right side). The error bars indicate standard deviations. The plus signs indicate results for the two individual measurements. wt, wild type.