FIG. 2.

Analysis of phagosome-lysosome fusion at 1.5 h postinfection by thin-section electron microscopy. J774A.1 cells were allowed to pinocytose 10-nm BSA-gold particles for 30 min. After 2.5 h of incubation to allow the gold particles to traffic through the endosomal pathway and to accumulate in lysosomes, the macrophages were infected with phoP⁺ or phoP mutant Y. pestis (MOI, 20) for 1.5 h. The infected macrophages were fixed and prepared for thin-section electron microscopy as described in Materials and Methods. (A) Phagosomes containing KIM5/GFP. (B) Phagosomes containing KIM5phoPΔ/GFP. Bacteria are indicated by asterisks. The arrows indicate gold particles in phagosomes.