IAI FigSearch
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Molmeret, M.
Right arrow Articles by Kwaik, Y. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Molmeret, M.
Right arrow Articles by Kwaik, Y. A.

 Previous Article  |  Next Article 

Infection and Immunity, July 2004, p. 4040-4051, Vol. 72, No. 7
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.7.4040-4051.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Disruption of the Phagosomal Membrane and Egress of Legionella pneumophila into the Cytoplasm during the Last Stages of Intracellular Infection of Macrophages and Acanthamoeba polyphaga

Maëlle Molmeret,1 Dina M. Bitar,2 Lihui Han,3 and Yousef Abu Kwaik1*

Department of Microbiology and Immunology, University of Louisville College of Medicine, Louisville, Kentucky 40292,1 Department of Microbiology and Department of Medical Microbiology and Immunology, Faculty of Medicine, Al-Quds University, Jerusalem 19356,2 Department of Microbiology and Immunology, College of Medicine, Shandong University, Jinan, Shandong, China 2500123

Received 29 October 2003/ Returned for modification 15 December 2003/ Accepted 14 March 2004

Although the early stages of intracellular infection by Legionella pneumophila are well established at the ultrastructural level, a detailed ultrastructural analysis of late stages of intracellular replication has never been done. Here we show that the membrane of the L. pneumophila-containing phagosome (LCP) is intact for up to 8 h postinfection of macrophages and Acanthamoeba polyphaga. At 12 h, 71 and 74% of the LCPs are disrupted within macrophages and A. polyphaga, respectively, while the plasma membrane remains intact. At 18 and 24 h postinfection, cytoplasmic elements such as mitochondria, lysosomes, vesicles, and amorphous material are dispersed among the bacteria and these bacteria are considered cytoplasmic. At 18 h, 77% of infected macrophages and 32% of infected A. polyphaga amoebae harbor cytoplasmic bacteria. At 24 h, 99 and 78% of infected macrophages and amoebae, respectively, contain cytoplasmic bacteria. On the basis of lysosomal acid phosphatase staining of infected macrophages and A. polyphaga, the lysosomal enzyme is present among the bacteria when host vesicles are dispersed among bacteria. Our data indicate that bacterial replication proceeds despite physical disruption of the phagosomal membrane. We also show that an lspG mutant that is defective in the type II secretion system and therefore does not secrete the hydrolytic enzymes metalloprotease, p-nitrophenol phosphorylcholine hydrolase, lipase, phospholipase A, and lysophospholipase A is as efficient as the wild-type strain in disruption of the LCP. Therefore, L. pneumophila disrupts the phagosomal membrane and becomes cytoplasmic at the last stages of infection in both macrophages and A. polyphaga. Lysosomal elements, mitochondria, cytoplasmic vesicles, and amorphous material are all dispersed among the bacteria, after phagosomal disruption, within both human macrophages and A. polyphaga. The disruption of the LCP is independent of the hydrolytic enzymes exported by the type II secretion system.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, Room 316, University of Louisville College of Medicine, 319 Abraham Flexner Way 55A, Louisville, KY 40202. Phone: (502) 852-4117. Fax: (502) 852-7531. E-mail abukwaik{at}louisville.edu.

Editor: J. T. Barbieri

Infection and Immunity, July 2004, p. 4040-4051, Vol. 72, No. 7
0019-9567/04/$08.00+0     DOI: 10.1128/IAI.72.7.4040-4051.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 2004 by the American Society for Microbiology. All rights reserved.