Figure 4.

Effect of medium osmolarity on biofilm formation by the WT and ΔtolC strains as determined by crystal violet biofilm assay. Both strains were cultivated in 1/2 M9 medium supplemented with different concentrations of NaCl (a) or sucrose (b) at 28°C for 5 days. Biofilm formation was quantified, and the results are shown as means ± standard error of the mean. Significant differences between the WT and ΔtolC strains were determined using one-tailed unpaired Student's t-test. ∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001; ∗∗∗∗P < 0.0001.