Figure 2. Eventual growth resumption of the ΔrelA strain in M9 is not due to compensatory mutations and its regrowth delay can be relieved by the addition of the full set of 20 amino acids.

(A) After 15 hours in stationary phase in M9 supplemented with 0.4% glucose (hereafter M9), cells were diluted into fresh M9 and grown until the stationary phase. After 15 hours in the second stationary phase cells were diluted into fresh M9 and the OD₆₀₀ of the second growth resumption of wild type (filled circles) and isogenic relaxed strain (empty circles) was followed. (B) The growth resumption delay of the ΔrelA culture disappeared upon addition of the full set of 20 amino acids (each at 100 μg/ml) to the outgrowth M9 medium. The ratio of OD₆₀₀ for ΔrelA to OD₆₀₀ of the wild type strain (red dotted line) serves as a numerical measure of the difference in growth resumption kinetics between the two. Results are shown as mean values of biological replicates (A, n = 2; B, n = 3) and error bars (too small to be seen for some of the points) indicate standard error of the mean.