Fig 2.

ppGpp influences lytic development of Shiga toxin-converting phages after infection. Lytic development of bacteriophages ϕ24B, 933W, P22, P27, and P32 after infection (at time zero) of E. coli strain MG1655 (triangles) and its relA (circles) and relA spoT (ppGpp⁰) (squares) derivatives, either unstarved (closed symbols) or starved for serine due to addition of serine hydroxamate to the culture up to 0.5 mg ml⁻¹ at time zero (open symbols), was studied. Diagrams show mean results from 3 experiments, with error bars indicating SD (note that in many cases the SD were smaller than sizes of symbols). The results are presented as PFU per infection center (IC). Statistical analysis (t test) was performed for results from each time point and indicated significant differences (P < 0.05) between unstarved wild-type and ppGpp⁰ hosts and between relA and ppGpp⁰ hosts but not between wild-type and relA, hosts for every phage at every time point after 100 min (but not at earlier times).