THE CELL BIOLOGY OF INFECTION BY INTRACELLULAR BACTERIAL PATHOGENS

Listeria monocytogenes and Shigella flexneri are unrelated bacterial p athogens that have independently evolved similar strategies of surviva l within an infected host animal. Bacteria coming into contact with th e surface of an epithelial cell induce cytoskeletal rearrangements res ulting in phagocytosis. They then secrete enzymes that degrade the pha gosomal membrane, releasing the bacteria into the host cell cytoplasm. Intracytoplasmic bacteria move rapidly, in association with a ''comet tail'' made up of host cell actin filaments. When moving bacteria rea ch the cell margin, they push out long protrusions with the bacteria a t the tips that are then taken up by neighboring cells, allowing the i nfection to spread from cell to cell. This review summarizes what is c urrently known about the interactions between the bacteria and the hos t at each stage of the infection and discusses what mammalian cell bio logists can learn by studying bacterial pathogens.