Fig. 2. (a) Longitudinal section through a L. pneumophila bacterium residing in a phagosome after 15 minutes of infection at an MOI of 20. The phagosome is surrounded by attached ER vesicles, many of which are the rough ER type (arrowheads point to attached ribosomes). The surface of the ER vesicles is flattened and smooth where it is attached to the phagosomal membrane but irregular in contour on its unattached surface. Even at this low magnification it is possible to detect tiny osmiophilic hairs at the attachment surface between the phagosomal and ER membranes. (b) Higher magnification view of the area outlined in (a). The hairs can be seen better in this micrograph (arrows). Note that by 15 minutes, the thickness of the phagosomal and ER membranes is the same, about 60 Å each.
