Fig. 3: (p)ppGpp induction negatively affects motility.

The ability of P. aeruginosa PA14 and PA01 to swim (A and C, respectively) or swarm (B and D, respectively) was determined in the presence of increasing serine hydroxamate (SHX) concentrations. Increase in the SHX concentration, associated with more severe induction of the stringent response, abolished both motility phenotypes. The experiments were repeated at least eight times and representative images of swimming and swarming motility agar plates are shown on the right side of each panel. The 50% inhibitory concentration (IC₅₀) of SHX was calculated by using the Hill equation. Significance was tested by using the Wilcoxon test (*P ≤ 0.05, **P ≤ 0.005, ***P ≤ 0.0005).