Figure 5. Ag43-dependent aggregation promotes resistance to oxidative stress and biofilm formation.

(a) Aggregation improves viability under oxidative stress conditions. Survival of the wild-type and Δflu cells on exposure to 0.5% H₂O₂ under aggregation (no shaking) or non-aggregation (shaking at 270 r.p.m.) conditions. Overexpression of LuxS does not rescue viability defect on the autoaggregation-defective Δflu strain. P value was calculated using Mann–Whitney test (***P<0.01). (b) Biofilm formation under static culture grown at 37 °C for 24 h, quantified using crystal violet (CV) staining. Shown in arbitrary units (a.u.) are CV values normalized by the optical density. P values were calculated using Mann–Whitney test (**P<0.05, NS, not significant, P>0.05). Error bars in a,b indicate s.d. of five independent replicates. (c) Confocal laser scanning microscopy of biofilms formed by the wild-type strain and by the aggregation-deficient mutants after 24 h static culture grown at 37 °C. Scale bars, 40 μm.