LAUSR

Staphylococcus aureus can cause infections that are often chronic and difficult to treat, even when the bacteria are not antibiotic resistant because most antibiotics act only on metabolically active cells. Subpopulations of persister cells are metabolically quiescent, a state associated with delayed growth, reduced protein synthesis, and increased tolerance to antibiotics. Serine-threonine kinases and phosphatases similar to those found in eukaryotes can fine-tune essential bacterial cellular processes, such as metabolism and stress signaling. We found that acid stress–mimicking conditions that S. aureus experiences in host tissues delayed growth, globally altered the serine and threonine phosphoproteome, and increased threonine phosphorylation of the activation loop of the serine-threonine protein kinase B (PknB). The deletion of stp, which encodes the only annotated functional serine-threonine phosphatase in S. aureus, increased the growth delay and phenotypic heterogeneity under different stress challenges, including growth in acidic conditions, the intracellular milieu of human cells, and abscesses in mice. This growth delay was associated with reduced protein translation and intracellular ATP concentrations and increased antibiotic tolerance. Using phosphopeptide enrichment and mass spectrometry–based proteomics, we identified targets of serine-threonine phosphorylation that may regulate bacterial growth and metabolism. Together, our findings highlight the importance of phosphoregulation in mediating bacterial quiescence and antibiotic tolerance and suggest that targeting PknB or Stp might offer a future therapeutic strategy to prevent persister formation during S. aureus infections. Description Acid-induced antibiotic tolerance in S. aureus depends on serine-threonine phosphorylation. Bacteria persist with Ser-Thr phosphorylation Subpopulations of non- or slow-growing persister cells enable bacteria to survive antibiotic treatment without specific resistance mechanisms. Huemer et al. investigated the role of serine-threonine phosphoregulation mediated by the kinase PknB and the phosphatase Stp in the persistence of antibiotic-susceptible Staphylococcus aureus. Acidic conditions similar to those experienced in host tissues delayed growth and promoted antibiotic tolerance, PknB activation, and serine-threonine phosphorylation of various proteins involved in proliferation, protein translation, and metabolism. The loss of Stp enhanced persistence and antibiotic tolerance in S. aureus that were grown under acidic conditions, cultured with human cells, or harvested from abscesses in mice. These findings identify signaling mediated by serine-threonine phosphorylation as contributors to S. aureus persistence and offer potential targets for combating chronic infections. –AMV