TABLE 1.

Bacterial strains and plasmids

Strain or plasmidRelevant propertiesSource
L. lactis
    MG1363Plasmid-free L. lactis subsp. cremoris NCDO71210
    FI9630MG1363 Δldh, food-grade strain30
    FI10021FI9630 carrying pVE6007, CmrThis work
    FI10022FI10021 carrying pFI2425, Eryr Cmr, blue on X-Gal platesThis work
    FI10089FI9630 ΔmtlF, food-grade strainThis work
    FI10090FI10021 carrying pFI2429, Eryr Cmr, blue on X-Gal platesThis work
    FI10091FI9630 ΔmtlA, food-grade strainThis work
Plasmids
    pGEM-TAmpr, cloning vectorPromega
    pVE6007Cmr plasmid providing RepA, temperature sensitive, only replicates at 30°C24
    pORI280Eryr lacZ+ ori+ of pWV01, replicates only in strains providing repA in trans19
    pFI2421Ampr derivative of pGEM-T vector containing mtlF upstream fragment generated by using primers MtlF1 and MtlF2This work
    pFI2422Ampr derivative of pGEM-T vector containing mtlF downstream fragment generated by using primers MtlF3 and MtlF4This work
    pFI2425Eryr, specific for deletion of the L. lactis mtlF geneThis work
    pFI2426Ampr derivative of pGEM-T vector containing 3.11-kb BamHI-BglII fragment generated by using primers MtlA1 and MtlA2This work
    pFI2427Ampr derivative of pFI2426 vector containing 2.04-kb BamHI-BglII fragment generated by deletion of 1.07-kb EcoRI-EcoRI portion inside the 3.11-kb fragmentThis work
    pFI2428Eryr Ampr derivative of pORI280 containing pFI2427 cloned into BamHI siteThis work
    pFI2429Eryr derivative of pFI2428 where pGEM-T portion has been deleted, specific for deletion of the L. lactis mtlA geneThis work