Fig 4.

Sensitivity of mutant isolates complemented with the maltose ABC transporter (malEFG) to GarML. Sensitivity is given as average fold changes in the MIC₅₀ relative to the respective controls (set to 1). The expression of malEFG was induced by the addition of nisin. Error bars show standard deviations from three biological replicates. (A) Sensitivity of GarML-resistant mutant isolates 200B1 and 150G1 complemented with the maltose ABC transporter (malEFG) at an induction level of 1 ng ml⁻¹ nisin relative to controls (empty vector). (B) Correlation between sensitivity to GarML and expression levels of the maltose ABC transporter in GarML-resistant mutant strain 200B3, with the induction level ranging from 0.1 to 10 ng ml⁻¹ relative to the control (no added nisin). No change in the MIC₅₀ was observed at concentrations below 1 ng ml⁻¹ nisin. A sharp decrease in the MIC₅₀ from 1 to 10 ng ml⁻¹ nisin is indicated by a power trend line (y = 0.942 x^−1.783; R² = 0.978).