Figure 1.

S. Typhimurium–encoded cspE is up-regulated during bile stress and is essential for resistance. A, transcript levels of cspA, cspB, and cspE were determined using qRT-PCR for the WT strain, under the indicated stress conditions, at the 3rd and 8th h of growth. The relative quantities of transcripts were calculated against the mean of the reference gene (rrlC). Transcript levels of target genes in the control set (WT cells grown in LB), at the 3rd and 8th h time point, were normalized to 1, and all other samples were calculated as fold-change to this reference value. B, kinetic growth analysis of WT and ΔcspE strains were analyzed in terms of CFU/ml over a period of 12 h of growth, in the absence (0%) or presence (3%) of bile salts. C, kinetic growth analysis, calculated in terms of CFU/ml WT/VA-, ΔcspE/VA-, and cspE-complemented (WT/pcspE and ΔcspE/pcspE) was studied for 12 h in the absence (0%) and presence (3%) of bile salts. Data are presented as mean ± S.E. and representative of three independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001; ****, p < 0.0001.