FIG 4 .

The transcription of pESI pilus is induced in response to microaerobiosis and physiological temperature and repressed by bile. (A) Semiquantitative reverse transcription-PCR analyses of pilV and 16S rRNA transcripts. RNA was extracted from S. Infantis 119944 cultures grown in LB, LB supplemented with 0.3 M NaCl, N-minimal medium (NMM) at pH 5.8, and N-minimal medium at pH 7.0. Templates of genomic DNA (gDNA) or purified RNA without reverse transcriptase treatment (−RT) were included as positive and negative controls, respectively. (B) qRT-PCR shows the fold change in pilV transcription under the same growth conditions as in panel A relative to the transcription of pilV in LB late-logarithmic culture grown under aerobic conditions. (C) Fold change in the transcription of pilV and pilT grown in LB under microaerobic conditions at 37 and 41°C relative to 27°C. (D) RNA was extracted from S. Infantis 119944 grown in LB and in LB supplemented with 0.1 mM H₂O₂ under microaerobic conditions at 37°C. qRT-PCR analysis was conducted to determine the fold change in the transcription of pilV. (E) Fold change in the transcription of pilV and pilT grown under microaerobic conditions at 37°C in LB supplemented with 4% bile salts (sodium choleate). All RT-PCR results show the mean and SD from three to six biological repeats. Two-tailed t test (B, D, and E) or one-way ANOVA with Tukey’s multiple comparison test (C) was implemented to determine statistical significance. *, P < 0.05; ***, P < 0.0001.