Figure 1
The outgrowth medium defines the growth resumption delay in ΔrelA E. coli strain.
The OD600 values of a wild type BW25113 strain (filled circles) and an isogenic ΔrelA strain (empty circles) were followed in LB (A, C and E, light beige shading) or M9 medium supplemented with 0.4% glucose (hereafter M9, light blue shading) (B,D,F). The ratio of OD600 for ΔrelA to OD600 of wild type strain (red dotted line) serves as a numerical measure of the difference in growth resumption kinetics between the two. Prior to inoculation, the seeder culture was kept for 15 hours in stationary phase in either LB (light beige shading) (A,D,E,F) or M9 (B,C) media. Cross-inoculation experiments M9-to-LB (C) and LB-to-M9 (D) demonstrate that the growth defect of ΔrelA is specific to the outgrowth medium, i.e. present only in M9. During the LB-to-M9 transition (D), cells were washed with M9 (indicated by the red triangle on the x axis) to reduce carry-over of medium. The washing procedure itself had only mild effect on cells and if anything, favored growth resumption of ΔrelA cells (E). Results are shown as mean values of biological replicates (n ≥ 3) and error bars (too small to be seen for some of the points) indicate standard error of the mean.
