Figure 5.

The (p)ppGpp⁰ mutant is less tolerant to stressors found within professional phagocytes. WT and (p)ppGpp⁰ were grown to OD₆₀₀ 0.35 in tryptic soy broth. Cells were washed twice in PBS and exposed to (A) 100 mM H₂O₂ or (B) 20 mM itaconic acid for 1 hour at 37°C before CFU determination. Statistical analysis performed using Mann-Whitney test. C and D, WT iTET, (p)ppGpp⁰ iTET, (p)ppGpp⁰ iTET-rel, and (p)ppGpp⁰ iTET-relP were grown to an OD₆₀₀ of 0.35. Cultures were washed twice in PBS and exposed to (C) 100 mM H₂O₂ or (D) 20 mM itaconic acid for 30 minutes at 37°C and the CFU/mL was determined. Percentage bacterial survival with mean and standard deviation are plotted. Statistical analysis performed using a Kruskal-Wallis test followed by a Dunn multiple comparison test. *P < .05, **P< .01. Abbreviations: (p)ppGpp⁰, guanosine tetraphosphate/guanosine pentaphosphate null mutant; CFU, colony-forming unit; OD₆₀₀, optical density at 600 nm; PBS, phosphate-buffered saline; WT, wild type.