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 Faulkner, G.
Right arrow Articles by Garduño, R. A.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Faulkner, G.
Right arrow Articles by Garduño, R. A.

 Previous Article  |  Next Article 

Journal of Bacteriology, December 2008, p. 7728-7738, Vol. 190, No. 23
0021-9193/08/$08.00+0     doi:10.1128/JB.00751-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Passage through Tetrahymena tropicalis Triggers a Rapid Morphological Differentiation in Legionella pneumophila{triangledown}

Gary Faulkner,1 Sharon G. Berk,2 Elizabeth Garduño,1 Marco A. Ortiz-Jiménez,3 and Rafael A. Garduño1,4*

Department of Microbiology & Immunology, Dalhousie University, Halifax, Nova Scotia, Canada,1 Center for the Management, Utilization and Protection of Water Resources, Tennessee Technological University, Cookeville, Tennessee,2 Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, D.F., Mexico,3 Department of Medicine, Division of Infectious Diseases, Dalhousie University, Halifax, Nova Scotia, Canada4

Received 26 May 2008/ Accepted 12 September 2008

The intracellular bacterial pathogen Legionella pneumophila follows a developmental cycle in which replicative forms (RFs) differentiate into infectious stationary-phase forms (SPFs) in vitro and in vivo into highly infectious mature intracellular forms (MIFs). The potential relationships between SPFs and MIFs remain uncharacterized. Previously we determined that L. pneumophila survives, but does not replicate, while it transiently resides (for 1 to 2 h) in food vacuoles of the freshwater ciliate Tetrahymena tropicalis before being expelled as legionellae-laden pellets. We report here that SPFs have the ability to rapidly (<1 h) and directly (in the absence of bacterial replication) differentiate into MIFs while in transit through T. tropicalis, indicating that SPFs and MIFs constitute a differentiation continuum. Mutant RFs lacking the sigma factor gene rpoS, or the response regulator gene letA, were unable to produce normal SPFs in vitro and did not fully differentiate into MIFs in vivo, further supporting the existence of a common mechanism of differentiation shared by SPFs and MIFs. Mutants with a defective Dot/Icm system morphologically differentiated into MIFs while in transit through T. tropicalis. Therefore, T. tropicalis has allowed us to unequivocally conclude that SPFs can directly differentiate into MIFs and that the Dot/Icm system is not required for differentiation, two events that could not be experimentally addressed before. The Tetrahymena model can now be exploited to study the signals that trigger MIF development in vivo and is the only replication-independent model reported to date that allows the differentiation of Dot/Icm mutants into MIFs.

* Corresponding author. Mailing address: Department of Microbiology & Immunology, Dalhousie University, Sir Charles Tupper Building, 7th floor, 5850 College Street, Halifax, Nova Scotia, Canada B3H-1X5. Phone: (902) 494-6575. Fax: (902) 494-5125. E-mail: Rafael.Garduno{at}dal.ca

{triangledown} Published ahead of print on 19 September 2008.

Journal of Bacteriology, December 2008, p. 7728-7738, Vol. 190, No. 23
0021-9193/08/$08.00+0     doi:10.1128/JB.00751-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Morash, M. G., Brassinga, A. K. C., Warthan, M., Gourabathini, P., Garduno, R. A., Goodman, S. D., Hoffman, P. S. (2009). Reciprocal Expression of Integration Host Factor and HU in the Developmental Cycle and Infectivity of Legionella pneumophila. Appl. Environ. Microbiol. 75: 1826-1837 [Abstract] [Full Text]  


Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»