FIGURE 2: The exponential cells of ppGpp⁰ strain are more persistent to ampicillin killing than the wt and ΔrelA strains. (A) Growth dynamics of the wt, ΔrelA and ppGpp⁰ strains in MOPSr-Lp. Four biological replicates were performed, and the averages and SDs are shown. (B) The ampicillin (250 μg/ml) killing curves of the exponentially growing wt, ΔrelA and ppGpp⁰ strains in MOPSr-Lp. Six biological replicates were performed, and the averages and SDs are shown. ΔrelA ΔspoT c1, c2, two separate colonies of the in-frame deletion mutants of both relA and spoT genes. **, p<0.01, student t-test, between ΔrelA and ppGpp⁰. (C) One representative plate of the surviving cells after ampicillin killing in panel B. (D) Growth dynamics of the wt, ΔrelA and ppGpp⁰ strains in MOPSr medium with the standard amount of phosphate. Two biological replicates were performed, and the averages and SDs are shown. (E) The ampicillin (250 μg/ml) killing curves of the exponentially growing wt, ΔrelA and ppGpp⁰ strains in MOPSr. Six biological replicates (MOPSr) were performed, and the averages and SDs are shown. For comparison, the same killing curves of the three strains from (B) were included.