Polyphosphate predicts and controls nanoparticle-induced antibiotic persistence

Nanoparticles (NPs) have emerged as promising agents against persistent bacterial infections. However, repeated exposure to NPs paradoxically leads to a significant increase in persister populations. This effect is linked to the accumulation of polyphosphate (polyP) granules at the cell poles. These polyP granules act as regulatory factors by binding to the Lon protease, inhibiting protein translation, and serving as metal homeostasis agents that chelate harmful intracellular metals. Our findings reveal a novel polyP-based mechanism underlying NP-induced persistence, suggesting innovative therapeutic targets to counteract bacterial survival and adaptive evolution in clinical settings. Overall design: Escherichia coli was cultured in LB medium at 37°C, 180 rpm, in the dark, until the stationary phase (20 h). A 1 mL cell suspension (108 CFU/mL) was collected and exposed to 30 mg/L AgNPs, 20 mg/L CuNPs, or 10 mg/L ZnO NPs. Another 1 mL cell suspension (107 CFU/mL) was collected and exposed to 100 mg/L Fe3O4 NPs, 100 mg/L CeO2 NPs, or 100 mg/L SiO2 NPs separately. The cells were then incubated in the dark for 4 h. After incubation, 100 µL of the mixture was transferred into 10 mL of fresh LB medium for a subsequent 20-h growth phase, completing one cycle. A total of 14 cycles were conducted. After 14 days of exposure to different NPs, the strains were named EAgNPs, ECuNPs, EZnO NPs, EFe3O4 NPs, ECeO2 NPs, and ESiO2 NPs. The ppk gene was knocked out in the EAgNPs strain, which was subsequently named EAgNPs(?ppk). Ewt represents the untreated control with no NP exposure.