Fig. 1.

Phenotypes associated with infection by the sidF mutant. (A) The sidF mutant formed fewer large phagosomes. Mouse macrophages were infected at an MOI of 1, and the distribution of vacuoles was determined at 14 h after infection as described (32). Strains tested are Lp02(intact dot/icm), Lp03(dotA⁻) (data not shown), Lp02ΔsidF, and Lp02ΔsidF harboring pZL623(pSidF). Data are from two independent experiments performed in triplicate, and >150 vacuoles were scored in each sample. (B) Mouse macrophages infected with a sidF mutant are more apoptotic. Uninfected cells and cells infected with Lp02(dot/icm intact), Lp03(dotA⁻), or Lp02(ΔsidF) and Lp02(ΔsidF/pSidF) for 14 h were fixed. Intracellular bacteria were labeled by indirect fluorescence staining with anti-L. pneumophila antibody, and the apoptotic status of the cells was probed by TUNEL staining. Samples were scored for fragmented chromatin by counting infected cells displaying positive TUNEL signals. Similar data were obtained from more than five independent experiments, and data from one representative experiment are shown.