Because a decrease in the transcription of fliC in the fliC-lux reporter correlates with a decrease in the luminescent signal, our data support the hypothesis that growth in the presence of PMs results in a reduction of fliC expression. As may be seen in Fig. 1a–c, the fliC gene is maximally expressed at 1 h after inoculation, which

agrees with reports from other groups (Lane et al., 2007a, b). To compare the effect of the different PMs on fliC expression, the maximal normalized luminescence of each treatment Etoposide was divided by the control conditions (Max. normalized luminescencetreatment/Max. normalized luminescencecontrol). This calculation revealed that PG, PGP, and PGRE, all at a concentration of 10%, reduced the normalized luminescence signal to 12%, 30%, and 8% of that of the control, respectively. Hence, we concluded that the strongest inhibitor find protocol of fliC expression in this study is the PGRE at a

concentration of 10%. To further assess the conditions under which PMs reduce fliC transcription, CFT073 PfliC-lux bacteria were grown in LB, harvested, resuspended in fresh media, and spiked with PGRE at different concentrations (0–10% v/v). Luminescence and OD600 were measured as described above and the normalized luminescence calculated. The maximum normalized luminescence, which was observed at 15 min after the PGRE addition, was plotted vs. the PGRE concentration and may be seen in Fig. 1d. The results obtained show that, relative to the control, a spike of PGRE reduces the normalized luminescence in a concentration-dependent manner. Based on

this data, we concluded that growth in PGRE is not necessary to achieve a reduction in the level of expression of the flagellin gene. To confirm that the reduced expression of fliC that results from growth in the presence of PMs decreases the production of flagellin, we conducted a Western blot analysis using H1 flagellin antiserum (Fig. 2a). This analysis confirmed that flagellin production declined when CFT073 was grown in LB supplemented with PMs because flagellin bands were observed only when the bacterium was grown under control conditions or when supplemented with 1% PGRE. For all other conditions tested, no bands were observed. Furthermore, as expected, no flagellin bands were observed on the blot in the lane also corresponding to the negative control, CFT073 ∆fliC. Additional validation of the observed decrease in flagellin production upon exposure to PGRE was obtained by imaging bacteria grown in LB with and without 10% PGRE using SEM. As shown in Fig. 2b–e, the bacteria grown in LB (Fig. 2b and c) had several flagella, whereas those grown in the presence of PGRE (Fig. 2d and e) exhibited few or no flagella. Next, we set out to evaluate whether the downregulation of fliC expression and corresponding drop in flagellin production that result from growth or exposure to PMs would impair bacterial motility.