TABLE 1

Bacterial strains and plasmids

Strain or plasmidRelevant genotype and/or phenotypeReference or source
Strains
    Lactobacillus rhamnosus
        GG (ATCC 53103)Wild type; human isolate21
        CMPG5357ΔspaCBA::Tcr; mutant of L. rhamnosus GG without spaCBA-encoded pili22
        CMPG5351ΔwelE::Tcr; mutant of L. rhamnosus GG without long galactose-rich exopolysaccharides but with increased exposure of pili20
        CMPG1908CMPG5357 with chromosomal insertion of pMEC10 in the attB sequence of phage mv4; EryrThis work
        CMPG1907CMPG5351 with chromosomal insertion of pMEC10 in the attB sequence of phage mv4; EryrThis work
        FAJ1906L. rhamnosus GG with chromosomal insertion of pFAJ1934 in the attB sequence of phage A2; Eryr33
    Lactococcus lactis subsp. cremoris
        MG1363Mesophilic lactic acid bacterium isolated from green plants30
        GRS1185L. lactis NZ9000 containing the nisin-inducible vector pKTH5080, which in turn contains the coding region of the spaCBA pilus operon; Cmr23
Plasmids
    pFAJ19342,634-bp PCR fragment (flanking EcoRI sites) carrying the nisRK genes of pMEC10 cloned into the EcoRI site of pEM40 downstream of the ery gene in the opposite orientation; Eryr Ampr33
    pMEC10Integration plasmid (attB located at the 3′ end of the tRNASer locus) containing the int-attP cassette (of phage mv4) of pMC1 cloned into pNZ9500 (a pUC19 derivative carrying a 2.7-kb chromosomal DNA fragment of L. lactis NZ9700 containing the 3′ end of nisP and nisRK); expression driven by ery read-through; Eryr34
    pMEC45L. lactis pSH71 replicon; pNZ8037 derivative with gfpuva cloned downstream of the nisA promoter from L. lactis NZ9800; Cmr36
  • a gfpuv, synthetic GFP gene (with improved codon usage) that was subsequently subjected to recurrent cycles of DNA shuffling, thereby selecting for bright fluorescence that can be observed under UV light.