Fig 4.

Mouse stomach transit competition experiments using STEC 88-0643 wild-type, Δure mutant, and Δure attTn7::ure complemented strains. Cultures of the strains to be tested were incubated separately overnight and administered to mice in a 1:1 ratio by oral gavage. The number of viable bacteria in the small intestine after 90 min was determined by selective plating. Percent survival rates were calculated and used to determine the competitive index. The competitive index for the wild-type/Δure mutant challenge was calculated to have a mean of 2.1 (horizontal bar), which was determined using the Student t test to be significantly different from a value of 1 (horizontal dashed line), with P = 0.0002. For the wild-type/Δure attTn7::ure challenge, the mean was 0.89 (horizontal bar), with P = 0.42, indicating that the mean is not significantly different from a value of 1.