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Chakraborty, S, Monfett, M, Maier, TM, Benach, JL, Frank, DW and Thanassi, DG (2008) Type IV pili in Francisella tularensis: roles of pilF and pilT in fiber assembly, host cell adherence, and virulence. Infect. Immun. 76:2852-61


Francisella tularensis, a highly virulent facultative intracellular bacterium, is the causative agent of tularemia. Genome sequencing of all F. tularensis subspecies revealed the presence of genes that could encode type IV pili (Tfp). The live vaccine strain (LVS) expresses surface fibers resembling Tfp, but it was not established whether these fibers were indeed Tfp encoded by the pil genes. We show here that deletion of the pilF putative Tfp assembly ATPase in the LVS resulted in a complete loss of surface fibers. Disruption of the pilT putative disassembly ATPase also caused a complete loss of pili, indicating that pilT functions differently in F. tularensis than in model Tfp systems such as those found in Pseudomonas aeruginosa and Neisseria spp. The LVS pilF and pilT mutants were attenuated for virulence in a mouse model of tularemia by the intradermal route. Furthermore, although absence of pili had no effect on the ability of the LVS to replicate intracellularly, the pilF and pilT mutants were defective for adherence to macrophages, pneumocytes, and hepatocytes. This work confirms that the surface fibers expressed by the LVS are encoded by the pil genes and provides evidence that the Francisella pili contribute to host cell adhesion and virulence.


PubMed PMC2446743 Online version:10.1128/IAI.01726-07


Adenosine Triphosphatases/chemistry; Adenosine Triphosphatases/genetics; Adenosine Triphosphatases/metabolism; Amino Acid Sequence; Animals; Bacterial Adhesion; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Bacterial Vaccines; Cells, Cultured; Fimbriae Proteins/chemistry; Fimbriae Proteins/genetics; Fimbriae Proteins/metabolism; Fimbriae, Bacterial/metabolism; Francisella tularensis/genetics; Francisella tularensis/metabolism; Francisella tularensis/pathogenicity; Hepatocytes/microbiology; Macrophages/microbiology; Mice; Mice, Inbred C3H; Molecular Motor Proteins/chemistry; Molecular Motor Proteins/genetics; Molecular Motor Proteins/metabolism; Molecular Sequence Data; Mutation; Oligonucleotide Array Sequence Analysis; Tularemia/microbiology; Tularemia/physiopathology; Vaccines, Attenuated; Virulence



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0009297: pilus assembly

IMP: Inferred from Mutant Phenotype:


Figure 3 shows that pilF mutants do not produce pili like the wild-type. When complemented with a plasmid containing the functional pilF gene, the mutant regains the ability to produce pili.

CACAO 8075


GO:0052001: Type IV pili-dependent localized adherence to host



Fig. 4; pilF mutants were significantly defective in adherence to host epithelial tissues when when compared to wild type cells and those that were complimented with pGPB.

CACAO 4872

See also


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