PersiSTRESS: How the stress-resistance antiporter GadC integrates bacterial osmoregulation and pH homeostasis with antibiotic-tolerant persistence

"What does not kill you makes you stronger" holds much truth in fighting bacterial infections. Indeed, many stress responses affect the illusive persister state that transforms cells to survive antibiotic treatment. Antibiotic persistence is present in all bacteria and not only prolongs treatment but also catalyses resistance development. As such, it is fundamental in the ongoing antibiotic crisis, yet remains overlooked and ill-understood especially when it comes to its relationship with stresses that bacteria frequent encounter. As main evolutionary target for antibiotic tolerance in Escherichia coli, I previously identified GadC, a transporter involved in acid resistance and osmoregulation. In PersiSTRESS, I will unravel the mechanism of GadC-dependent antibiotic tolerance. First, I will examine how osmotic and acidic stress influence antibiotic tolerance in gadC*-mutants and find the underlying genetic networks using CRISPRi-Seq. Second, I will biochemically characterize the GadC variants carrying high-persistence mutations. Third, integrating phenotypic, genetic, and biochemical results, I will examine the physiology of gadC*-mutants using single-cell fluorescence cytometry and microscopy. To end, I will proof the concept that GadC-dependent tolerance is widespread and relevant in an in vivo model. As a milestone in the field, PersiSTRESS will align stress responses with antibiotic tolerance and might give us the upper hand to kill the strongest among bacterial cells.