(p)ppGpp-mediated GTP homeostasis ensures the survival and antibiotic tolerance of Staphylococcus aureus during starvation by preserving the proton motive force

Upon nutrient limitation bacteria enter a nongrowing state, which allow bacterial survival and antibiotic tolerance. The mechanisms whether and how the messenger molecule (p)ppGpp contributes to the transition in Firmicutes is debated. Here we show for Staphylococcus aureus that (p)ppGpp-dependent restriction of the GTP pool is essential for the culturability of starved cells and for antibiotic tolerance. Elevated GTP levels in a starving (p)ppGpp-deficient mutant lead to a division-incompetent, dormant state characterized by reduced metabolic activity and alterations in membrane function and architecture. GTP level control of nucleotide sensitive promoters result in transcriptional downregulation of gene of the TCA cycle and electron transport chain. Increasing transcription of qoxABCD, a terminal oxidase of the respiratory chain, through mutation of the transcriptional start site partially restored the culturability of the (p)ppGpp-deficient mutant. Furthermore, we showed that the maintenance of proton motive force under nutritional stress contributes to antibiotic tolerance, supporting the idea of applying (p)ppGpp or PMF inhibitors to combat antibiotic-tolerant bacteria.