title: The effects of inhibitors of vacuolar acidification on the release of Listeria monocytogenes from phagosomes of Caco-2 cells.
abstract: To evaluate the role of the acidic pH of phagosomes on the invasive ability and fate of Listeria monocytogenes within host cells, entry and replication of this gram-positive bacterium in a human enterocyte-like cell line (Caco-2) were investigated by a combination of biochemical and ultrastructural approaches. The effects of inhibitors of vacuolar acidification--the lipophilic weak base ammonium chloride, the carboxylic ionophore monensin and the vacuolar proton ATPase inhibitor bafilomycin A1--on the bacterial invasion pathway were analysed. These agents, which raise the intracellular vesicle acidic pH of living cells by different mechanisms, affected L. monocytogenes replication in Caco-2 cells. Bacteria internalised by bafilomycin-treated cells were unable to escape from phagosomes, as demonstrated by electronmicroscopy. The results provide evidence that low pH is required for efficient intracellular growth of L. monocytogenes.
authors.affiliation: Microbiology Institute, University of Rome, La Sapienza, Italy.
authors.forename: M P
authors.initials: MP
authors.lastname: Conte
authors.forename: G
authors.initials: G
authors.lastname: Petrone
authors.forename: C
authors.initials: C
authors.lastname: Longhi
authors.forename: P
authors.initials: P
authors.lastname: Valenti
authors.forename: R
authors.initials: R
authors.lastname: Morelli
authors.forename: F
authors.initials: F
authors.lastname: Superti
authors.forename: L
authors.initials: L
authors.lastname: Seganti
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018938:Caco-2 Cells / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells / Q000382:microbiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects / Q000502:physiology*; D018942:Macrolides; D008854:Microscopy, Electron; D008985:Monensin / Q000494:pharmacology; D010588:Phagosomes / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D007476:Ionophores; D018942:Macrolides; D000643:Ammonium Chloride; C040929:bafilomycin A1; D008985:Monensin; D006180:Proton-Translocating ATPases