Role of FliF and FliI of Listeria monocytogenes in flagellar assembly and pathogenicity.
Flagellar structures have been shown to participate in virulence in a variety of intestinal pathogens. Here, we have identified two potential flagellar genes of Listeria monocytogenes: lmo0713, encoding a protein similar to the flagellar basal body component FliF, and lmo0716, encoding a protein similar to FliI, the cognate ATPase energizing the flagellar export apparatus. Expression of fliF and fliI appears to be downregulated at 37 degrees C, like that of flaA, encoding flagellin. By constructing two chromosomal deletion mutants, we show that inactivation of either fliF or fliI (i) abolishes bacterial motility and flagella production, (ii) impairs adhesion and entry into nonphagocytic epithelial cells, and (iii) also reduces uptake by bone marrow-derived macrophages. However, the DeltafliF and DeltafliI mutations have only a minor impact on bacterial virulence in the mouse model, indicating that the flagellar secretion apparatus itself is not essential for survival in this animal model. Finally, among 100 human clinical isolates of L. monocytogenes tested, we found 20 strains still motile at 37 degrees C. Notably, all these strains adhered less efficiently than strain EGD-e to Caco-2 cells at 37 degrees C but showed no defect of intracellular multiplication. These data suggest that expression of the flagella at 37 degrees C might hinder optimal adhesion to epithelial cells but has no impact on intracytosolic survival of L. monocytogenes.
Bigot
Armelle
A
Faculté de Médecine Necker, 156 rue de Vaugirard, 75730 Paris Cedex 15, France.
Pagniez
Hélène
H
Botton
Eléonore
E
Fréhel
Claude
C
Dubail
Iharilalao
I
Jacquet
Christine
C
Charbit
Alain
A
Raynaud
Catherine
C
D000818:Animals; D001422:Bacterial Adhesion / Q000235:genetics; D001426:Bacterial Proteins / Q000502:physiology*; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D005407:Flagella / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D005408:Flagellin / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008089:Listeria monocytogenes / Q000472:pathogenicity / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D009154:Mutation; D011499:Protein Processing, Post-Translational; D006180:Proton-Translocating ATPases / Q000502:physiology*; D017422:Sequence Analysis, DNA; D013696:Temperature
D001426:Bacterial Proteins; C075661:Flif protein, Bacteria; D008565:Membrane Proteins; D005408:Flagellin; C067138:flaA protein, bacteria; C069251:fliI protein, bacteria; D006180:Proton-Translocating ATPases