PMC

Quorum sensing in the P. aeruginosa ppk mutant. (A) Bioassays of AI-1 and AI-2 (average ± SEM of six measurements in three separate experiments). (B) Elastase activity and rhamnolipid amount (average ± SEM of three measurements) in P. aeruginosa culture supernatants determined by elastin Congo red and oricinol assays, respectively. (C) Expression of the lasB-lacZ and the rhlA-lacZ fusion constructs contained in plasmids in the ppk mutant. β-Galactosidase activity (average ± SEM of three measurements) was measured as described in Materials and Methods. Strains are as in Fig. .

Biofilms of P. aeruginosa WT and ppk mutant strains in static cultures (A, B, and D) and flow-through continuous cultures (C). (A and B) Degree of surface attachment of bacteria at 8 h (A) and at 20 h (B) by staining with crystal violet (average ± SEM of four measurements). (C) Height of biofilms (in μm) (average ± SEM for 75 measurements in three separate experiments) and surface area coverage of biofilms (as percentage of total flow-cell area) (average ± SEM of 15 measurements in three separate experiments). (D) Epifluorescence and SCLM of static biofilms of the WT and ppk mutant containing the GFP expression vector pMRP9–1 (). The top view epifluorescence micrographs were taken (with a X60 lens) at 5 μm from the substratum. Bar is 10 μm. The side views were acquired by SCLM (with a X20 lens). Bar is 50 μm. Bacterial cells contain GFP and the color intensity correlates with cell density. Strains: WT, PAO1; ppk, PAOM5; and ppk (PPK⁺⁺⁺), PAOM5 containing pHEPAK11.