Fig. 1

Overview of the ALE process and improved PA tolerance. Three conditions were used for the ALE experiment: minimal medium (pH 5); buffered minimal medium (pH 3.5); buffered minimal medium with increasing concentrations of PA (pH 3.5). Three independent cultures were grown under each condition (a). Growth rates of PA-evolved populations sampled through ALE were determined in buffered minimal medium containing 25 mM PA (b) and 35 mM PA (c). Growth rates of isolates from end-point PA-evolved populations (PA-1, PA-2, PA-3, PA-4, and PA-5) were determined in buffered minimal medium containing 35 mM PA. “Medium” represents the isolate from end-time minimal medium-evolved population (d). Bars and error bars represent the mean and standard deviation (SD) of triplicate cultures