Original Paper

Archives of Microbiology

, Volume 194, Issue 12, pp 977-989

FliA expression analysis and influence of the regulatory proteins RpoN, FleQ and FliA on virulence and in vivo fitness in Legionella pneumophila

  • Tino SchulzAffiliated withCellular Interactions of Bacterial Pathogens, Centre for Biological Security, Division 2 (ZBS2), Robert Koch-Institute
  • , Kerstin RydzewskiAffiliated withCellular Interactions of Bacterial Pathogens, Centre for Biological Security, Division 2 (ZBS2), Robert Koch-Institute
  • , Eva SchunderAffiliated withCellular Interactions of Bacterial Pathogens, Centre for Biological Security, Division 2 (ZBS2), Robert Koch-Institute
  • , Gudrun HollandAffiliated withCentre for Biological Security, Division 4 (ZBS4), Robert Koch-Institute
  • , Norbert BannertAffiliated withCentre for Biological Security, Division 4 (ZBS4), Robert Koch-Institute
  • , Klaus HeunerAffiliated withCellular Interactions of Bacterial Pathogens, Centre for Biological Security, Division 2 (ZBS2), Robert Koch-Institute Email author 

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Abstract

In Legionella pneumophila, the regulation of the flagellum and the expression of virulence traits are linked. FleQ, RpoN and FliA are the major regulators of the flagellar regulon. We demonstrated here that all three regulatory proteins mentioned (FleQ, RpoN and FliA) are necessary for full in vivo fitness of L. pneumophila strains Corby and Paris. In this study, we clarified the role of FleQ for fliA expression from the level of mRNA toward protein translation. FleQ enhanced fliA expression, but FleQ and RpoN were not necessary for basal expression. In addition, we identified the initiation site of fliA in L. pneumophila and found a putative σ70 promoter element localized upstream. The initiation site was not influenced in the ΔfleQ or ΔrpoN mutant strain. We demonstrated that there is no significant difference in the regulation of fliA between strains Corby and Paris, but the FleQ-dependent induction of fliA transcription in the exponential phase is stronger in strain Paris than in strain Corby. In addition, we showed for the first time the presence of a straight hook at the pole of the non-flagellated ΔfliA and ΔfliD mutant strains by electron microscopy, indicating the presence of an intact basal body in these strains.

Keywords

Legionella pneumophila Paris Corby Flagellin regulation FleQ FliA RpoN Virulence In vivo fitness Straight hook