Fig. 3.
Expression of S. typhi cdtB after growth in vitro or after infection of cultured cells. (A) A S. typhi strain (control) and an isogenic derivative encoding a cdtB::luc reporter fusion were grown in LB broth to an OD600 of 1.0, and the luciferase activity in total cell lysates was measured as described in Materials and Methods. (B) Alternatively, cultured intestinal Henle-407 cells were infected with the S. typhi cdtB::luc reporter strain, and the luciferase activity at different times after infection was measured as indicated in Materials and Methods. In all cases, values were standardized relative to the colony-forming units and the values obtained in cells 2.5 h after infection, which was considered 100%.