Virulence Conversion of Legionella pneumophila by Conjugal Transfer of Chromosomal DNA

Hiroshi Miyamoto, Shin Ichi Yoshida, Hatsumi Taniguchi, Howard A. Shuman

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

In this study, we examined whether virulence conversion occurs in Legionella pneumophila by conjugal transfer of chromosomal DNA. A virulent strain, K6, which has the genes for Kmr and LacZ+ transposed in the chromosome of strain Philadelphia-1, which belongs to serogroup 1, was used as one parent, and an avirulent strain, Chicago-2S, which is a spontaneous streptomycin-resistant derivative of strain Chicago-2 belonging to serogroup 6, was used as the other parent. Experiments in which K6 (approximately 2.6 × 109 CFU) and Chicago-2S (approximately 8. 9 × 109 CFU) were mated typically yielded 103 Kmr Smr LacZ+ transconjugants. Thirty-two (about 2.8%) of 1,152 transconjugants belonging to serogroup 6 acquired the ability to grow intracellularly in Acanthamoeba castellanii and guinea pig macrophages. When guinea pigs were infected with sublethal doses of Legionella aerosols generated from one of these transconjugants (HM1011), they developed a severe pneumonia similar to that caused by donor strain K6. These results show that avirulent strain Chicago-2S changed into virulent strain HM1011 through conjugation with virulent strain K6. Furthermore, we showed that Legionella chromosomal virulence genes (icm-dot locus) were horizontally transferred by the conjugation system. The chromosomal conjugation system may play a role(s) in the evolution of L. pneumophila.

Original languageEnglish
Pages (from-to)6712-6718
Number of pages7
JournalJournal of bacteriology
Volume185
Issue number22
DOIs
Publication statusPublished - Nov 1 2003

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Legionella pneumophila
Virulence
Legionella
DNA
Guinea Pigs
Acanthamoeba castellanii
Philadelphia Chromosome
Lac Operon
Streptomycin
Aerosols
Pneumonia
Macrophages
Genes
Serogroup

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

Cite this

Virulence Conversion of Legionella pneumophila by Conjugal Transfer of Chromosomal DNA. / Miyamoto, Hiroshi; Yoshida, Shin Ichi; Taniguchi, Hatsumi; Shuman, Howard A.

In: Journal of bacteriology, Vol. 185, No. 22, 01.11.2003, p. 6712-6718.

Research output: Contribution to journalArticle

Miyamoto, Hiroshi ; Yoshida, Shin Ichi ; Taniguchi, Hatsumi ; Shuman, Howard A. / Virulence Conversion of Legionella pneumophila by Conjugal Transfer of Chromosomal DNA. In: Journal of bacteriology. 2003 ; Vol. 185, No. 22. pp. 6712-6718.
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