fob phagosomes fail to mature. Double-labeled bacteria were allowed to internalize for 10 min (broken line) or 30 min (solid line), and images were captured for 15 min. The distribution of fluorescence ratios is shown for Ore-R (A) and fob1 (B). The fluorescence ratio relates to pH as shown in Fig. S1. (C) Electron micrographs of phagosomes detected after a 30-min chase of phagocytosed E. coli. Phagosomal structures were broadly classified in three categories based on their ultrastructural appearance: phagosome (C), late phagosome (C′) and phagolysosomes (C′′). Bar, 1 µm. (D) Relative distribution of different categories of phagosomes in Ore-R and fob1. Data were collected from two independent sets of experiments with equivalent results. Quantification was performed in triplicate with a representative example shown in D.
