Fig. 6.

Effect of acrB deletion on growth under high ethanol stress. (a) The graph shows the growth of both the wild-type strain and the acrB deletion mutant under 5.5% ethanol stress. The ΔacrB mutant grows faster and reaches a higher carrying capacity (higher final optical density) under these conditions. (b) The growth curves were fitted using the Gompertz equation (see Materials and Methods) and specific growth rate was extracted. The acrB deletion mutant has a significantly increased growth rate compared with the wild type. Both growth rates were statistically compared using an unpaired two-sided Student’s t test (n = 6, box = median, whiskers = min to max, ****P <  0.0001). These results confirm a selective advantage of the ΔacrB mutant compared with the wild type.