FIG 5.

dif and lpg1867 deletion strains exhibit filamentation and altered growth on solid media and during infection of host cells. (A) DAPI-stained cells of the indicated L. pneumophila strains showing filamentation upon deletion of the dif site or lpg1867 and rescue when recA is deleted in the Δlpg1867 background. The scale bars represent 10 μm. Frequency of filamentation was quantified using the MicrobeJ plugin for ImageJ (58) and is shown in the right panel. (B, left panel) CYET spread plates after 4 days of growth at 37°C with visible differences in colony size. (Right panel) Each colony radius is plotted as a separate data point, with the geometric mean shown by the purple line. (C) Distribution of colony sizes in the 5-deletion strain and pan-deletion strain (left panel) and in the pan-deletion strain expressing wild-type or mutant Lpg1867 (right panel). Data are plotted as in panel B. (D) Intracellular growth of wild-type and deletion strains in U937 macrophages. The data are plotted as the fold increase in CFU recovered after lysis from host cells at 2 h and 48 h postinfection relative to wild-type Lp02. Data show the average of three replicates for each strain from a representative experiment. Error bars represent SEM.