Salmonella Choleraesuis ∆crp is more resistant to low pH or bile salts. Bacteria grown to stationary phase in LB broth were incubated for 1 h in M9 medium at pH 3.0 or 7.0 (A) or in saline, 15% bile salts, or 1% sodium deoxycholate (B). Survival of bacteria before and after incubation was determined on MacConkey agar plates. Percent survival was normalized to the initial inoculum. WT, wild type Salmonella Choleraesuis; CP327 and CP359, crp gene mutants; Comp., CP327 complemented with pTCRP plasmid; BS, bile salts; DOC, sodium deoxycholate. The results are from three independent experiments of at least triplicate determinations. Error bars are SEM. *p < 0.05; ***p < 0.001; n.s.: no significant difference from each other (ANOVA).