Figure 5.

Recovery of tetracycline resistance of (p)ppGpp-deficient strains under anaerobic and iron-deplete conditions. A–F, tetracycline resistance of N16961 (circles), (p)ppGpp⁰ mutant (triangles), and ΔdksA mutant (squares) strains under anaerobic conditions. Wildtype N16961 and various (p)ppGpp-associated mutant strains were inoculated in LB and aerobically grown to each growth stage. Aliquots of each culture were resuspended in several concentrations of antibiotic-containing LB broth and incubated for 4 h in anaerobic conditions. Each aliquot was sampled and 10-fold serially diluted to assess the number of cfu. G–L, tetracycline resistance of N16961 and (p)ppGpp-deficient mutant strains under iron-depleted conditions. Aliquots of each culture were resuspended in several concentrations of tetracycline-containing LB supplemented with 2,2′-dipyridyl, sampled at 4 h post-inoculation, and serially diluted for cfu counting.