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Journal of Bacteriology, May 2005, p. 2927-2938, Vol. 187, No. 9
0021-9193/05/$08.00+0     doi:10.1128/JB.187.9.2927-2938.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

The DotL Protein, a Member of the TraG-Coupling Protein Family, Is Essential for Viability of Legionella pneumophila Strain Lp02

Benjamin A. Buscher,1,{dagger} Gloria M. Conover,2,{dagger} Jennifer L. Miller,1 Sinae A. Vogel,1 Stacey N. Meyers,1 Ralph R. Isberg,2,3 and Joseph P. Vogel1*

Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110,1 Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111,2 Howard Hughes Medical Institute, Tufts University School of Medicine, Boston, Massachusetts 021113

Received 6 July 2004/ Accepted 20 January 2005

Legionella pneumophila is able to survive inside phagocytic cells by an internalization route that bypasses fusion of the nascent phagosome with the endocytic pathway to allow formation of a replicative phagosome. The dot/icm genes, a major virulence system of L. pneumophila, encode a type IVB secretion system that is required for intracellular growth. One Dot protein, DotL, has sequence similarity to type IV secretion system coupling proteins (T4CPs). In other systems, coupling proteins are not required for viability of the organism. Here we report the first example of a strain, L. pneumophila Lp02, in which a putative T4CP is essential for viability of the organism on bacteriological media. This result is particularly surprising since the majority of the dot/icm genes in Lp02 are dispensable for growth outside of a host cell, a condition that does not require a functional Dot/Icm secretion complex. We were able to isolate suppressors of the {Delta}dotL lethality and found that many contained mutations in other components of the Dot/Icm secretion system. A systematic analysis of dot/icm deletion mutants revealed that the majority of them (20 of 26) suppressed the lethality phenotype, indicating a partially assembled secretion system may be the source of {Delta}dotL toxicity in the wild-type strain. These results are consistent with a model in which the DotL protein plays a role in regulating the activity of the L. pneumophila type IV secretion apparatus.

* Corresponding author. Mailing address: Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110. Phone: (314) 747-1029. Fax: (314) 362-3203. E-mail: jvogel{at}borcim.wustl.edu.

{dagger} B.A.B. and G.M.C. contributed equally to this study.

Journal of Bacteriology, May 2005, p. 2927-2938, Vol. 187, No. 9
0021-9193/05/$08.00+0     doi:10.1128/JB.187.9.2927-2938.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Vincent, C. D., Buscher, B. A., Friedman, J. R., Williams, L. A., Bardill, P., Vogel, J. P. (2006). Identification of Non-dot/icm Suppressors of the Legionella pneumophila {Delta}dotL Lethality Phenotype. J. Bacteriol. 188: 8231-8243 [Abstract] [Full Text]  
  • Perez, B. A., Planet, P. J., Kachlany, S. C., Tomich, M., Fine, D. H., Figurski, D. H. (2006). Genetic Analysis of the Requirement for flp-2, tadV, and rcpB in Actinobacillus actinomycetemcomitans Biofilm Formation.. J. Bacteriol. 188: 6361-6375 [Abstract] [Full Text]  


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