FIGURE 3.

L. monocytogenes intracellular life cycle. (a) Listeria invades the host cells via a zipper mechanism, by the interaction of surface internalins InlA and InlB with the host cell surface receptors E-cadherin and Met, respectively. (b) Listeria escapes from the phagosome before the fusion with the lysosome occurs, by the action of the secreted proteins, the pore-forming toxin LLO, and phosphatidylinositide phospholipase C (PI-PLC). (c) Listeria may replicate in the cytosol, and (d) it spreads by actin polymerization, which propels the bacteria unidirectionally, (e) promoting cell-to-cell spreading of Listeria. (f) Rupture of the two-membrane vacuole is mainly mediated by the action of LLO and phosphatidylcholine-specific phospholipase C (PC-PLC).