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Journal of Bacteriology, November 2003, p. 6269-6277, Vol. 185, No. 21
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.21.6269-6277.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Molecular Evolution of the dotA Gene in Legionella pneumophila

Kwan Soo Ko,1,{dagger} Seong Karp Hong,1 Hae Kyung Lee,2 Mi-Yeoun Park,2 and Yoon-Hoh Kook1*

Department of Microbiology and Cancer Research Institute, Institute of Endemic Diseases, SNUMRC, Seoul National University College of Medicine, and Clinical Research Institute, Seoul National University Hospital, Seoul 110-799,1 Laboratory of Rickettsial and Zoonotic Disease, Department of Microbiology, Korean National Institute of Health, Seoul 122--701, Korea2

Received 19 May 2003/ Accepted 11 August 2003

The molecular evolution of dotA, which is related to the virulence of Legionella pneumophila, was investigated by comparing the sequences of 15 reference strains (serogroups 1 to 15). It was found that dotA has a complex mosaic structure. The whole dotA gene of Legionella pneumophila subsp. pneumophila serogroups 2, 6, and 12 has been transferred from Legionella pneumophila subsp. fraseri. A discrepancy was found between the trees inferred from the nucleotide and deduced amino acid sequences of dotA, which suggests that multiple hits, resulting in synonymous substitutions, have occurred. Gene phylogenies inferred from three different segments (the 5'-end region, the central, large periplasmic domain, and the 3'-end region) showed impressively dissimilar topologies. This was concordant with the sequence polymorphisms, indicating that each region has experienced an independent evolutionary history, and was evident even within the same domain of each strain. For example, the PP2 domain was found to have a heterogeneous structure, which led us hypothesize that the dotA gene of L. pneumophila may have originated from two or more different sources. Comparisons of synonymous and nonsynonymous substitutions demonstrated that the PP2 domain has been under strong selective pressure with respect to amino acid change. Split decomposition analysis also supported the intragenic recombination of dotA. Multiple recombinational exchange within the dotA gene, encoding an integral cytoplasmic membrane protein that is secreted, probably provided increased fitness in certain environmental niches, such as within a particular biofilm community or species of amoebae.

* Corresponding author. Mailing address: Department of Microbiology, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-799, Korea. Phone: (82) 2-740-8306. Fax: (82) 2-743-0881. E-mail: yhkook{at}plaza.snu.ac.kr.

{dagger} Present address: Infectious Disease Research Institute, Asian-Pacific Research Foundation for Infectious Diseases (ARFID), Seoul, Korea.

Journal of Bacteriology, November 2003, p. 6269-6277, Vol. 185, No. 21
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.21.6269-6277.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Edwards, M. T., Fry, N. K., Harrison, T. G. (2008). Clonal population structure of Legionella pneumophila inferred from allelic profiling. Microbiology 154: 852-864 [Abstract] [Full Text]  
  • Aurell, H., Farge, P., Meugnier, H., Gouy, M., Forey, F., Lina, G., Vandenesch, F., Etienne, J., Jarraud, S. (2005). Clinical and Environmental Isolates of Legionella pneumophila Serogroup 1 Cannot Be Distinguished by Sequence Analysis of Two Surface Protein Genes and Three Housekeeping Genes. Appl. Environ. Microbiol. 71: 282-289 [Abstract] [Full Text]  


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