FIG. 2.

L. pneumophila bacteria expressing mutant alleles of AnkB are rescued within cells harboring the wild-type bacteria. Coinfections were performed using the wild-type L. pneumophila strain AA100 and the ankB mutant or using the ankB mutant harboring one of the mutant alleles ankBΔA1, ankBΔA2, and ankBΔA1A2. Infected U937 cells were gentamicin treated, washed, and fixed at 10 h after infection. Bacterial phagosomes were scored for all infected cells in randomly selected fields by confocal microscopy. Cells harboring phagosomes containing both strains (WT-GFP [green fluorescent protein] and a mutant) were scored. The htrA mutant was used as a negative control while the dotA mutant was used as a positive control. Representative confocal images are shown in panel A, while quantitative analyses are shown in panel B. Rescue was calculated by quantifying the percentage of the cells harboring the ankB mutant replicating within cells harboring the WT strain, and the numbers are shown in the merged images. The results are representative of three independent experiments performed in triplicate by analyses of 100 infected cells. Error bars represent standard deviations.