Role of RelA-synthesized (p)ppGpp in de novo acquisition of antibiotic resistance in E. coli

Abstract

Abstract The stringent response of bacteria to starvation and stress, also fulfils a role in addressing the threat of antibiotics. Within this stringent response, (p)ppGpp, synthesized by RelA or SpoT, functions as a global alarmone. However, the effect of this stringent response and (p)ppGpp on resistance development is poorly understood. Here, we show that the knockout of relA or rpoS curtails resistance development against bactericidal antibiotics. The emergence of mutations in genes such as the starvation protection factor dps, and another (p)ppGpp synthase spoT in ΔrelA-resistant strains, indicates the activation of stringent responses. The growth rate is decreased in ΔrelA-resistant strains due to the reduced ability to synthesize (p)ppGpp and the persistence of deacylated tRNA impeding protein synthesis. Sluggish cellular activity leads to decreased production of reactive oxygen species (ROS), which in turn diminishes the oxidative damage, specifically the generation of 8-hydroxy-2'-deoxyguanosine (8-HOdG), leading to the attenuation of DNA repair. Collectively, this contributes to the deceleration of resistance development under long-term antibiotic treatment. This study substantiates the intricate interplay between RelA-synthesized (p)ppGpp and ROS-mediated mutagenesis in resistance development. These findings offer new targets for mitigating antibiotic resistance development, potentially achieved through the inhibition of (p)ppGpp or ROS synthesis.