Figure 1

Fis participates in down-regulation of hlyE expression in S. Typhi. A) RT-PCR assay for mRNAs examining transcription of the hlyE gene from S. Typhi wild-type (STH2370), Δcrp, Δfis, Δcrp Δfis double mutant, and the complemented strains Δcrp/pTCRP and Δfis/pTFIS. All the strains were cultured as described in Methods. *p < 0.05; **p < 0.01 (ANOVA). B) Relative hemolysis, obtained from the S. Typhi STH2370 wild type, Δfis and Δcrp mutants. All the strains were grown in LB and samples were taken to perform the hemolytic activity quantification (see Methods). The total hemolytic activity was calculated deducting relative hemolysis of S. Typhi ΔhlyE[10] from S. Typhi wild type, deducting relative hemolysis of S. Typhi ΔhlyE Δfis from S. Typhi Δfis or S. Typhi ΔhlyE Δcrp from S. Typhi Δcrp, respectively. C) Relative hemolysis, obtained from the S. Typhi STH2370 wild type, Δfis and Δcrp mutants grown in LB + 0.4% glucose. Hemolysis was calculated as described in B. D) Immunodetection of epitope-tagged HlyE from S. Typhi hlyE-3xFLAG (par.: parental strain), S. Typhi hlyE-3xFLAG Δcrp, and S. Typhi hlyE-3xFLAG Δfis. Bacteria were cultured as described in Methods. E) RT-PCR for fis transcript levels detection in S. Typhi wild type strain grown to logarithmic phase in LB or LB + glucose. In all the cases, the data correspond to mean values of three independent experiments performed in triplicate. Error bars correspond to the SD.