Fig. 5: OmpA mediates HNP1-promoted biofilm formation by A. baumannii.

A Adhesion of three 19606 strains on A549 cells evaluated by the bacterial adhesion assay. The cells were washed with DMEM, incubated with 19606 in the presence or absence of HNP1 for 2 h, lysed with water, diluted with PBS, and then plated on LB agar for colony counting after overnight culture. B Effect of HNP1 on biofilm formation of three 19606 strains. Upper panel: Biofilm formation in 96-well plates quantified by CV staining. Lower panel: Biofilm formation on the air-liquid interface of polystyrene tubes stained with CV. HNP1 did not enhance bacterial adhesion to A549 cells (A) or biofilm formation (B) in the ompA knockout mutant (ΔOmpA), but these effects were restored with ompA complementation (ΔOmpA:C). Results of A and B are mean ± SD representative of at least two experiments (n = 6 biological replicates per experiment). C Visualization using fluorescent microscopy of biofilm formation on silicone surfaces by three A. baumannii 19606 strains with/without HNP1, stained by PI (Scale bar = 50 μm), representative of two independent experiments. D Visualization using SEM of biofilm formation on silicone surfaces by A. baumannii 19606 WT and ΔOmpA strains with/without HNP1 (Scale bar = 50 μm), representative of two biological replicates. E Competitive inhibition of exogenously added recombinant OmpA on HNP1-promoted biofilm formation. Results are pooled mean ± SD of three independent experiments (n = 3 biological replicates per experiment). Statistical significances (A, B and E) were evaluated by two-way ANOVA with Tukey correction for multiple comparison. See also Supplementary Figs. S7 and S8.