FIG 3.
Stx2 production by EDL933 in the presence or absence of vitamin K analogs. Stx2 production under H2O2-induced (A), ciprofloxacin-induced (B), and MMC-induced (C) conditions, in the presence or absence of menadione, MSB, menaquinone, or phylloquinone, was measured by LC-MS/MS. The error bars represent the SD from three independent experiments. An asterisk indicates statistically significant difference (P < 0.05) in Stx2 levels compared to negative-control cultures with the same inducing agent and same solvent as those used for solubilization of the vitamin K variants, i.e., DMSO or water. *, P < 0.05; **, P < 0.01; ***, P < 0.001 (Student's t test).