FIG. 1.

Vi capsule expression detected by flow cytometry. Cells of the S. Typhi wild type (A), an S. Typhi ΔtviB-vexE mutant (B), E. coli strain W3110 (C), E. coli strain W3110 carrying the cloned viaB locus (pDC5) (D), an S. Typhi vexE mutant (E), or an S. Typhi vexE mutant complemented with the cloned vexE gene (pAS1) (F) were labeled with rabbit anti-Vi serum/goat-anti rabbit FITC conjugate (Vi expression, y axis), and fluorescence intensities were determined for 10,000 particles. Each experiment was repeated three times independently with similar outcomes, and a representative example is shown.