FIG 5.

Quantification of LAMP-1 colocalization with F. tularensis strain SCHU S4. J774 cells were infected for 1 h with the indicated F. tularensis strains at an MOI of 30 or latex beads at an MOI of 10, and after washing, they were further incubated for up to 18 h. Fixed samples were labeled for the late endosomal/lysosomal marker LAMP-1. (A) Percentages representing the fractions of F. tularensis- or latex bead-containing phagosomes stained for the late endosomal/lysosomal marker LAMP-1. (B) A separate analysis was performed for strain FSC043 at 18 h. LAMP-1 colocalization was determined for two populations of bacteria observed in infected host cells: (i) a majority (95%) of J774 cells with individual bacteria (designated PI) and (ii) a minority (5%) of J774 cells with clusters of replicating bacteria (designated PII). The results are expressed as mean values and SD from one representative experiment in which 100 bacteria each on triplicate coverslips were counted. The asterisks indicate colocalization levels significantly different from those of SCHU S4 for each time point. *, P < 0.05; ***, P < 0.001, according to a t test. Experiments were repeated 2 to 4 times for the 0- and 3-h time points and twice for the 18-h time point.