Hydrogen Peroxide Affects Growth of S. aureus Through Downregulation of Genes Involved in Pyrimidine Biosynthesis

Abstract

Reactive oxygen species (ROS) play a crucial role in the cellular defense against S. aureus, as evidenced by the importance of this pathogen in patients lacking the ROS-generating phagocyte NADPH oxidase NOX2. ROS concentrations required to kill S. aureus in vitro are much higher than those found in the phagosome. We therefore hypothesized that sublethal ROS concentrations may play a role in S. aureus gene dysregulation and investigated the in vitro transcriptomic response of S. aureus to sublethal concentrations of hydrogen peroxide (H2O2). A striking observation of these experiments was a coordinated and massive downregulation of genes involved in pyrimidine metabolism. Using transposon insertion mutants, we demonstrated that deletion of carA, a gene involved in pyrimidine synthesis, led to a significant growth defect and to an increased sensitivity of S. aureus to added H2O2. The phenotype of the carA mutant could be reversed through supplementation with the pyrimidine precursor uracil, or with a multicopy vector encoding carA. As opposed to the impact of ROS on extracellular survival, carA deletion did not affect the intracellular survival in neutrophils. Our results raise the possibility that ROS-dependent downregulation of pyrimidine metabolism might be a survival strategy of S. aureus, allowing colonization through intracellular survival, while decreasing the risk of killing the host through dampened extracellular growth.

Pyrancoumarin derivative LP4C targeting of pyrimidine de novo synthesis pathway inhibits MRSA biofilm and virulence

“…The genes involved in pyrimidine ribonucleotide biosynthesis were involved with most donw-regulated pathway. pyr genes such as pyrP , pyrB , pyrC , carA , carB , pyrF and pyrE , were located on the same operon and transcribed from a single promoter regulated by pyrR-mediated transcriptional attenuation ( Turnbough and Switzer., 2008 ; Buvelot et al, 2021 ). We investigated whether LP4C downregulates pyr genes by targeting the PyrR protein.…”

Hyperglycemia increases the severity ofStaphylococcus aureusosteomyelitis and influences bacterial genes required for survival in bone

“…19 Furthermore, carA is critical for S. aureus extracellular survival in the presence of high H 2 O 2 . 44 Purine and pyrimidine synthesis enable S. aureus to persist in the presence of hydroxyl radicals that oxidize base and ribose moieties of DNA, creating lesions that require repair. 45 The gene ccpA was also uniquely essential for S. aureus growth during osteomyelitis in hyperglycemic mice, linking the abundance of glucose in tissues with transcriptional control of genes involved in gluconeogenesis, the TCA cycle, and cell adherence and immune evasion.…”

Fluid flow sensitizes bacterial pathogens to chemical stress

“…Thus, the minimum concentration necessary to elicit a flow-sensitive response at a shear rate of 800 sec -1 is approximately 4 µM H2O2 (Figure 4A). Surprisingly, 4 µM is 100-1000 times lower than the H2O2 concentration traditionally studied in batch cell culture 24,[32][33][34][35][36] . Moreover, the H2O2 concentration in the human bloodstream is thought to be between 1 and 5 µM 37 .…”

“…Our discovery that bacteria in flow are sensitive to H2O2 concentrations that are 100-1000 times lower than traditionally used should provoke a paradigm shift in the way we think about H2O2 stress. For simplicity, studies on H2O2 stress in bacteria have primarily used batch cell cultures and millimolar amounts of H2O2 24,[32][33][34][35][36] . However, natural environments are unlikely to contain such high H2O2 concentrations 9 .…”