FIG. 5.

Effect of catechin on exogenous addition of homoserine lactones. (A) Effect of catechin on the perception of C4-HSL by RhlR. The pAL101 and pAL102 E. coli biosensor strains were incubated for 8 h with DMSO (1% [vol/vol]), catechin (4 mM), C4-HSL only (10 μM), or C4-HSL (10 μM) plus catechin (4 mM). Samples were taken to record the luminescence of the culture in relative light units (RLU) and to measure the OD₆₀₀. The pAL102 strain was used as background. The statistical significance of each test (n = 6) was evaluated by conducting Student t tests, and a P value of ≤0.01 was considered significant. (B and C) Production of pyocyanin (B) and elastase (C) by the wild-type strain PAO1 after the addition of C4-HSL or 3-oxo-C12-HSL (10 μM) in the presence or absence of catechin after 8 h of incubation. Pyocyanin (A₃₈₀) and elastase (A₄₉₅) were quantified as described in Materials and Methods, and values were corrected for the difference in cell density (OD₆₀₀). (D) Pyocyanin production in the ΔrhlI mutant (PA3476) after the addition of C4-HSL or 3-oxo-C12-HSL (10 μM) in the presence or absence of catechin after 8 h of incubation. ***, Data that are statistically different (P ≤ 0.01). The different letters above the histograms indicate that the data are statistically different from each other (P ≤ 0.01).