TABLE 1.

Bacterial strains and plasmids used in this study

Strain or plasmidCharacteristics or descriptionaReference or sourceb
Strains
    E. coli S17-1thi thr leu tonA lacY supE recA::RP4-2-Tc::Mu Kn::Tn736
    F. novicida strain U112Avirulent strainWater, 1950, Utah (16, 19)
    F. tularensis subsp. tularensis SchuS4Virulent type AHuman ulcer, 1941, Ohio; FSC237
    F. tularensis subsp. holarctica HN63Virulent type BHare, 1963, Telemark, Norway; FSC092
Plasmids
    pSMP22Suicide vector for allelic replacements in F. tularensis, constructed based on pPV2 (a gift from I. Golovliov) (15). CHL resistance gene was removed by digestion with HindIII, and the plasmid backbone was religated. A F. tularensis groES promoter with sacB fusion cassette was cloned into the SalI/MluI sites.This study
    pSMP22-RT1Suicide plasmid used to inactivate O-antigen cluster of F. tularensis subsp. tularensis; 2.5-kb fragment cloned into pSMP22; CHL resistance cassette inserted between amplified fragments of F. tularensis subsp. tularensis wbtD and wbtF genes.This study
    pSMP22-RT2Suicide plasmid used to inactivate O-antigen cluster of F. novicida; 2.5-kb fragment cloned into pSMP22; CHL resistance cassette inserted between amplified fragments of F. novicida wbtDFn and wbtFFn genes.This study
  • a CHL, chloramphenicol.

  • b Identifiers are from the Francisella Strain Collection (FSC) in Umeå, Sweden.