FIG. 1.

The blp_St locus of S. thermophilus and study of the functionality of bacteriocin production in S. thermophilus. (A) Schematic representation of the blp_St locus in strains CNRZ1066 (genes str1691 to str1673), LMG18311 (stu1691 to stu1673), and LMD-9 (STER_1634 to STER_1653). Genes encoding peptides with predicted functions are represented by patterned arrows as follows: ABC transporter, small squares; transport accessory protein, large squares; response regulator, vertical lines; HK, horizontal lines; bacteriocin-like peptide, light gray; inducing factor, dark gray; hydrophobic peptide of unknown function, black; hydrophilic peptide of unknown function, white; peptide similar to the immunity protein SakI_X of the Class IIa bacteriocin sakacin X, chess squares) (46); and modification protein, points. Genes encoding peptides with a 2-Gly leader are represented by gray arrows (light and dark). Letters and numbers in italics refer to the corresponding blp genes and orf genes, respectively. (B) Detection of bacteriocin production using the spot-on-lawn method from strains LMD-9 (pGILF002), CNRZ1066 (pGILF001), and LMG18311 (pGILF001) overexpressing their cognate blpC_St gene. Strains carrying the empty expression vector (pMG36e) are used as control or indicator strains. Five microliters of culture (OD₆₀₀ of 1) of each producer strain (names of strains and their corresponding numbers are indicated on the right) was spotted directly on a soft agar layer containing 10⁸ CFU of the indicator strain (names of strains are indicated above each picture).