FIGURE 2.

Strategies employed by pathogens to subvert or adapt to the acidic phagosomal pH. (A) Phagosome maturation leads to luminal acidification and subsequent killing of the internalized prey. (B) Mycobacteria and Salmonella enterica arrest phagosome maturation by impairing endo-lysosome insertion into the maturing phagosome. (C) Legionella pneumophila secretes into the host cytosol the effector sidK that binds and inhibits H⁺ pumping by the V-ATPase, leading to impaired acidification. (D) Listeria monocytogenes secretes the pore-forming toxin listeriolysin O and phospholipases, leading to a rupture of the phagosomal membrane. (E) Candida albicans survives and grows as filaments inside the acidic phagosome. The C. albicans-containing phagosome expands and remains acidic for hours before permanent rupture causes H⁺ leakage.