Fig. 3

Effect of MNQ, or in combination with tetracycline on the biofilm formation and maturation. E. coli DH5α + pAM401-tet(X4) biofilms were grown for 24 h with the presence or absence of MNQ and/or tetracycline (TET) (a–c). Additionally, the indicated concentrations of MNQ and/or TET were subsequently added at 12 h post-inoculation for an additional 12 h-incubation to assess the disruption of preformed E. coli biofilms by MNQ or the combinations (d–f). The graphs presented the OD_{570 nm} values of crystal violet (CV)-staining biofilms (a, d) and biomass (CFUs) quantified by the microbiological plating (b, e). c, f Confocal microscopy images of E. coli biofilms grown with or without MNQ and/or TET. Fluorescence intensity of each sample represents biofilms thickness. The representative image was chosen from three independent replicates. All data were repeated three times independently. **P < 0.01 and *P < 0.05 vs. the control group; ^##P < 0.01 vs. MNQ monotherapy group