Fig. 2.

Effects of farnesol on the levels of pqsH transcript and C4HSL. (a) RT-PCR analysis of strains PA14ΔlasR and PA14ΔlasRrhlR : : TetR colonies grown in the absence (black bars) and presence (grey bars) of 250 μM farnesol. The levels of pqsH and ppiD were measured in control colonies and colonies grown in the presence of farnesol for 12 h. While there is variability in the biological replicates within an experiment, likely due to the fact that quorum-sensing-controlled genes are rapidly changing in colonies at these time points, statistically significant increases in pqsH in the presence of farnesol were observed in four independent experiments. Data presented represent three biological replicates from one independent experiment (mean±sd). *P<0.1 based on Student's t-test. (b) C4HSL levels were measured from PA14ΔlasR and PA14ΔlasRrhlR : : TetR colonies grown for 10 h in the absence (black bars) and presence (grey bars) of 250 μM farnesol. Levels were determined by luciferase activity generated by the reporter plasmid pSB536, which detects short-chain AHLs, verified by comparison with a titrated authentic C4HSL standard and reported as relative luminescence units (RLU) after normalization to levels in control cultures. Error bars, sd.