Figure 6

HQNO from P. aeruginosa stimulates biofilm production of S. aureus strains by a SigB-dependent mechanism. (A) Growth curves of P. aeruginosa strain PA14 and the pqsA and pqsL mutants. (B) Pictures show relative biofilm production of CF1A-L in the absence or in the presence of supernatants from overnight cultures of P. aeruginosa PA14 or the pqsL mutant as determined by crystal violet staining. (C) Relative biofilm production by S. aureus CF1A-L as a function of the proportion of supernatant from overnight cultures of P. aeruginosa PA14, the pqsA mutant, the pqsL mutant or E. coli K12. Results are normalized to unexposed CF1A-L (dotted line). Significant differences between CF1A-L+PA14 and the other conditions for each proportion of supernatant are shown (*, P < 0.05; two-way ANOVA with Bonferroni's post test). (D) Relative biofilm production by S. aureus strains Newbould and NewbouldΔsigB as a function of the proportion of supernatant from overnight cultures of P. aeruginosa PA14, the pqsA or the pqsL mutant. Significant differences between Newbould + PA14 and the other conditions for each proportion of supernatant (*, P < 0.05; two-way ANOVA with Bonferroni's post test), and between NewbouldΔsigB + PA14 and Newbould ΔsigB + the pqsA or the pqsL mutant (Δ, P < 0.05; two-way ANOVA with Bonferroni's post test) are shown. The significant difference between untreated Newbould and NewbouldΔsigB is also shown (#, P < 0.05; unpaired t-test). Data are presented as means with standard deviations from at least three independent experiments.