TABLE 1

Bacterial strains and plasmids used in this study

Strain or plasmidDescription and sourceReference or source
Strains
    Y. pestis
        CO92Virulent WT Y. pestis biovar Orientalis strain isolated in 1992 from a fatal pneumonic plague case and naturally resistant to polymyxin B36, 37
        Δlpp CO92lpp gene deletion mutant of Y. pestis CO9223
        Δpla CO92pla gene in-frame deletion mutant of Y. pestis CO92This study
        Δlpp Δpla CO92lpp and pla gene double deletion mutant of Y. pestis CO92This study
        CO92(pBR322)WT Y. pestis transformed with pBR322 (Tcs)35
        CO92 Δlpp(pBR322)CO92 Δlpp mutant transformed with pBR322 (Tcs)35
        CO92 Δpla(pBR322)CO92 Δpla mutant transformed with pBR322 (Tcs)This study
        CO92 Δlpp Δpla(pBR322)CO92 Δlpp Δpla double mutant transformed with pBR322 (Tcs)This study
        CO92 Δpla (pBR322Ypla)Y. pestis pla deletion mutant complemented via plasmid pBR322Ypla (Tcs)This study
        Δlpp Δpla (pBR322Ypla)Y. pestis lpp and pla double deletion mutant complemented via plasmid pBR322Ypla (Tcs)This study
    E. coli SM10Strain containing the λpir gene (lysogenized with λpir phage) designed for cloning and propagation of a plasmid with the R6K origin of replication38
Plasmids
    pBR322Cloning vector for complementation (Tcr Apr)GE Healthcare
    pKD13Template plasmid for PCR amplification of the Kmr gene cassette flanked by FLP recombinase recombination target sites39
    pFlp2Vector that produces the FLP recombinase to remove the Kmr gene cassette from the mutant40
    pDMS197Suicide vector with a conditional R6K origin of replication (ori) and a levansucrase gene (sacB) from Bacillus subtilis used for homologous recombination41
    pBR322YplaRecombinant plasmid containing the pla gene-coding region and its putative promoter in vector pBR322 used to complement the Δpla mutant of Y. pestis (Tcs)This study
    pDMS197plaUDKmSuicide vector pDMS197-based recombinant plasmid containing the Y. pestis CO92 pla gene up- and downstream flanking DNA fragments with the Kmr cassette used for homologous recombinationThis study