Fig. 7. Co-infection of U937 cells with two bacteria; L. pneumophila, a Gram-negative bacterium and a second Gram-positive bacterium are depicted here in this thin section of a phagosome. No ER vesicles attach themselves to the phagosome of the Gram-positive species. The thickness of the phagosomal membrane remains the same as the plasma membrane, 70 Å. This bacterium will be killed subsequently in a lysosome.