Attenuated virulence of a Francisella mutant lacking the lipid A 4'-phosphatase.

Journal Article (Journal Article)

Francisella tularensis causes tularemia, a highly contagious disease of animals and humans, but the virulence features of F. tularensis are poorly defined. F. tularensis and the related mouse pathogen Francisella novicida synthesize unusual lipid A molecules lacking the 4'-monophosphate group typically found in the lipid A of Gram-negative bacteria. LpxF, a selective phosphatase located on the periplasmic surface of the inner membrane, removes the 4'-phosphate moiety in the late stages of F. novicida lipid A assembly. To evaluate the relevance of the 4'-phosphatase to pathogenesis, we constructed a deletion mutant of lpxF and compared its virulence with wild-type F. novicida. Intradermal injection of 10(6) wild-type but not 10(8) mutant F. novicida cells is lethal to mice. The rapid clearance of the lpxF mutant is associated with a stronger local cytokine response and a greater influx of neutrophils compared with wild-type. The F. novicida mutant was highly susceptible to the cationic antimicrobial peptide polymyxin. LpxF therefore represents a kind of virulence factor that confers a distinct lipid A phenotype, preventing Francisella from activating the host innate immune response and preventing the bactericidal actions of cationic peptides. Francisella lpxF mutants may be useful for immunization against tularemia.

Full Text

Duke Authors

Cited Authors

  • Wang, X; Ribeiro, AA; Guan, Z; Abraham, SN; Raetz, CRH

Published Date

  • March 6, 2007

Published In

Volume / Issue

  • 104 / 10

Start / End Page

  • 4136 - 4141

PubMed ID

  • 17360489

Pubmed Central ID

  • PMC1820721

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.0611606104


  • eng

Conference Location

  • United States