Table 1.
Bacterial strains.
Table 2.
Bacteriocin-producing and non-producing strains used in this study.
Table 3.
Susceptibility to nisin A, nukacin ISK-1 and bacitracin of S. aureus mutants.
Figure 1.
Expression of TCSs and ABC transporters in S. aureus exposed to nukacin ISK-1.
Analysis of expression levels of braR, graR, vraR, braA, vraD, and vraF were performed as described in the Materials and Methods. (A) braA, vraF, vraD, braR, graR, and vraR expression in S. aureus MW2 exposed to various concentrations of nukacin ISK-1 (5-min exposure). *, statistically significant difference from the wild-type as tested using Dunnett’s method (p<0.05). (B) Time course experiment of braA, vraF, and vraD expression in S. aureus MW2 exposed to nukacin ISK-1 (4 µg/ml). (C) braA, vraF, and vraD expression in S. aureus MW2 and three mutants (braRS, graRS, and vraSR mutant) exposed to nukacin ISK-1 (4 µg/ml). *, statistically significant difference from the wild-type as tested using Dunnett’s method (p<0.05).
Figure 2.
Co-culture of S. aureus with S. warneri
The co-culture experiment was performed with the method described in the Materials and Methods. (A) Percent ratio of the S. aureus population when mixed with various concentrations of S. warneri ISK-1 and nukacin-non-producing S. warneri. (B) Expression of the ABC transporters (braA and vraD) when mixed with various concentrations of S. warneri ISK-1. *p<0.05, as determined by Dunnett’s method for the expression of the ABC transporters (braA and vraD).
Figure 3.
Co-culture of S. aureus TCS and transporter mutants with S. warneri or L. lactis.
The co-culture assay is described in the Materials and Methods. A 100-µl aliquot of S. warneri ISK-1 (108 cells/ml) (A) or L. lactis ATCC 11454 (108 cells/ml) (B) was mixed with 100 µl of S. aureus (107 cells/ml for S. warneri and 106 cells/ml for L. lactis). (C) Expression of the ABC transporter vraDE in the mutants when mixed with S. warneri ISK-1 or L. lactis. *p<0.05, as determined by Dunnett’s method for the percent ratio of the S. aureus population and the expression of the ABC transporters.
Table 4.
Susceptibility of bacitracin-treated and vraDE-overexpressing S. aureus to nisin A and nukacin ISK-1.
Figure 4.
Association of TCSs and ABC transporters with susceptibility to class I bacteriocins, nisin A and nukacin ISK-1.