FIG. 4.
Denitrification regulation by rhl and las quorum-sensing systems. (A) Effect of 10 μM C4-HSL and 1 μM 3-oxo-C12-HSL on a ΔrhlI ΔlasI double mutant. The amounts of NO3− reduced and N2 produced over 12 h were measured. Solid bars, NO3− reduced; open bars, N2 produced. Data are means ± standard deviations from three independent experiments. (B) Effects of 10 μM C4-HSL and 1 μM 3-oxo-C12-HSL on the transcription of denitrifying genes in a ΔrhlI ΔlasI mutant. C23O activity was measured in cells cultured for 6 h (late-exponential phase). Data are means ± standard deviations from three independent experiments.