Fig. 3.
Contact-mediated virulence is rapidly induced and requires quorum sensing but not growth. (A and B) Composite phase contrast and calcein-AM fluorescence images (A) and host killing indexes (gray bars) and corresponding P. aeruginosa cell densities (white bars; B; see SI Appendix, SI Materials and Methods for details) for P. aeruginosa that were surface-attached for 1 h at midexponential (OD600 = 0.3 or 0.5) or late-exponential (OD600 = 0.9) growth phases and mixed with amoebae. (C) Host killing indexes for P. aeruginosa that were treated with antibiotics during surface attachment at late-exponential phase. (D and E) Composite phase contrast and calcein-AM fluorescence images (D) and host killing indexes (E) for WT and ΔlasR (quorum-sensing defective) cells. (F) Host killing indexes of planktonic P. aeruginosa cells that were supplemented with DMSO or quorum-sensing autoinducers (QS AI). Bars represent the average of at least two independent experiments, and error bars indicate SD. (Scale bars: 50 µm.)