FIG. 3.

Fur is required for efficient intestinal colonization. For each competition, the indicated strains were grown under the conditions described and coinoculated intragastrically into 5-day-old BALB/c mice, as detailed in Materials and Methods. The competitive index was calculated by normalizing the output ratio to the input ratio of the two competing strains. Each data point represents one mouse, and the average competitive index for each experimental group is represented by a horizontal line. A competitive index below 1 (shown by the dashed line) indicates that the fur mutant is at a competitive disadvantage. Three experimental groups are shown. Group 1 and group 3 strains were grown in LB broth, pH 7, at 37°C to mid-log phase prior to inoculation, while group 2 strains were grown in low-salt LB broth, pH 6.5, at 30°C (TCP-inducing conditions) to mid-log phase prior to inoculation.