Figure 4. The mreB^A53T allele confers a lag-phase growth advantage.

A) Population growth dynamics for the ancestor and the mreB^A53T strain in Davis minimal medium plus glucose (DM+Glu). Optical density (OD) is normalized by the initial optical density (OD_i). Errors represent standard error (n = 6). B) Time-lapse images of the mreB^A53T strain and the ancestor transitioning from stationary phase to exponential growth in DM+Glu medium. Ancestral and mreB^A53T genotypes were distinguished based on differences in cell width, which have well separated distributions (Fig. 1 & Table S1). Red arrows indicate mreB^A53T cells and blue arrows indicate ancestral cells. C) Instantaneous growth rates of single cells transitioning from stationary phase to exponential growth on DM+Glu indicate a decrease in lag phase time for mreB^A53T cells. Growth rates were calculated as the fractional increase in the two-dimensional projected area of the cell between frames. Shaded boundaries represent standard error (n = 20). D) Fine-scale analysis of differential growth for the mreB^A53T strain competed against the ancestor in the Glu environment. Competitive differential growth represents the natural log difference in growth between competitors relative to their initial density. As a control, the ancestor was also competed against itself and showed no growth differences over the course of competition. Error bars represent standard error (n = 8).