Fig. 1

Sensitivity of C. glutamicum to nisin. A Membrane damage of C. glutamicum CR099/pPB-pHin2^Cg biosensor in the presence of different concentrations of nisin. Values are ratios of fluorescence intensity with emission at 510 nm after excitation at 400 and 470 nm (ratio RFU 400/470). B Optical density (OD₆₀₀) of C. glutamicum CR099/pEKEx2 and CR099ΔporAΔporHΔporB/pEKEx-vraDE after 24 h of incubation in the presence of nisin at the indicated concentrations (195–12,500 ng/ml). For assays bacteria were harvested from fresh o/N cultures, resuspended in fresh medium at an OD₆₀₀ of 0.05 in 2xTY medium. For CR099ΔporAΔporHΔporB/pEKEx-vraDE, medium was additionally supplemented with 2 g/l CaCl₂. All values are mean ± standard deviation (SD) of triplicate measurements of one representative of three independent cultures per strain. The red and green lines indicate OD₆₀₀ or ratio RFU 400/470 of the positive (i.e. complete inhibition of growth) or negative (i.e. in the absence of nisin) control, respectively