Serine-threonine phosphoregulation by PknB and Stp contributes to quiescence and antibiotic tolerance in Staphylococcus aureus

Abstract

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.

Loratadine Combats Methicillin-Resistant Staphylococcus aureus by Modulating Virulence, Antibiotic Resistance, and Biofilm Genes

“…aureus, the overall number of phosphopeptides in the cell increased, especially in ribosomal proteins and elongation factors. This led to a decrease in the overall protein synthesis and an increase in antibiotic tolerance compared to the wild-type strain . Although that report cannot be directly compared to ours (they examined differentially expressed proteins, not genes, and they used deletion mutants, not an inhibitory molecule like loratadine), the results are intriguing because of the high degree of overlap in affected target genes/proteins.…”

Progress in the Prevalence, Classification and Drug Resistance Mechanisms of Methicillin-Resistant Staphylococcus aureus

“… 122 Phosphatase Stp also impacted antibiotic resistance because Stp deletion strains are more susceptible to cell wall-acting antibiotics like tunicamycin, fosfomycin and β-lactam antibiotics, and Stp contributes to reduced susceptibility to vancomycin. 123 …”

Transcriptomic Analysis of Loratadine as an Antibiotic Adjuvant Against MRSA

“…This led to a decrease in overall protein synthesis and an increase in antibiotic tolerance compared to the wildtype strain. 38 While that report cannot be directly compared to ours (they examined differentially expressed proteins, not genes, and they used deletion mutants, not an inhibitory molecule), the results are intriguing because of the high degree of overlap in affected target genes/proteins. We found that loratadine reduced stp mRNA levels (Supporting Information Table S4), and in those cells, the downregulated genes were overrepresented with ribosomal genes.…”