FIGURE 1.

Luteolin inhibits LLO production at the translational level by directly targeting the coding region of hly. (A) The hemolytic activity in culture supernatants of Listeria monocytogenes following coculture with various concentrations of luteolin. (B) The growth of L. monocytognes in the presence of various concentration of luteolin. (C) Western blot analysis of LLO production in culture supernatants and bacterial pellets following luteolin treatment. (D,E) hly transcription in L. monocytogenes was not inhibited by luteolin. Bacteria were cocultured with various concentrations of luteolin, and the transcription of hly was evaluated by RT-PCR. (F) L. monocytogenes-lacZ fusions were cultured in TSB agar supplemented with X-gal and kanamycin at 37°C for 48 h to determine the effect of the tested compounds on hly transcription. Wells 1 to 5 contained 6.99, 13.98, 27.95, 55.90, and 111.80 μM luteolin, respectively; well 6 contained DMSO; and well 7 contained bromo-geramine. (G) The effect of luteolin on LLO and PLY production (transcription and translation) in a cell-free system. (H) The activity of luteolin in inhibiting LLO translation. hly mRNA was synthesized using a T7 RiboMAX Express Large-Scale RNA Production System and further used for the determination of LLO translation with an E. coli S30 Extract System for Linear Templates following luteolin treatment. The data are expressed as the mean ± SEM (n = 3). ^∗∗P < 0.01.