FIG. 2.

Compilation of phospholipase and cytotoxic activities for all ExoU-LINKER molecules. Supernatants containing ExoU-LINKER molecules secreted from P. aeruginosa were used to determine phospholipase activity in a fluorescence-based ExoU activity assay. ExoU-LINKER molecules are categorized as either active or inactive based on PED6 cleavage after 2 h (top half). Every ExoU-LINKER strain was tested for cytotoxicity as determined by loss of a crystal violet-stained HeLa cell monolayer. After a 4-h infection, the HeLa cell monolayers were fixed and stained as outlined in Materials and Methods. The stain was solubilized with 95% ethanol, and the absorbance was recorded at 570 nm. Each ExoU-LINKER molecule is categorized as being positive or negative for crystal violet retention (bottom half).