The sRNA-encoded peptide TimP rewires the Escherichia coli envelope via LamB to sensitize bacteria to polymyxins

The rise of multidrug-resistant (MDR) Escherichia coli has marginalized last-line polymyxins (PMs) owing to evolving resistance and narrow therapeutic windows. Revitalizing these agents requires the identification of novel regulatory circuits governing the integrity of the gram-negative envelope. In this study, we identified a stress-responsive peptide TimP and demonstrated that its intracellular overexpression (TimP⁺), a synthetic variant (FT-Pep), and biogenic TimP⁺-derived extracellular vesicles (TimP EVs) exhibited equivalent functionality in sensitizing E. coli to PMs, consistently inducing PM-mediated phenotypes. Mechanistically, TimP in E. coli initiates coordinated envelope remodeling by interacting with porin LamB via a specific _N21TimP-_R134LamB molecular interface. Furthermore, the TimP-TimR/TimP-LamB interaction is functionally conserved in both E. coli and Salmonella. Pharmacokinetic profiling and spatiotemporal imaging of FT-Pep revealed a predictable physiological disposition across major organs and gradual systemic clearance over 24 h, with no evidence of pathological sequestration. Hepatic and immunological assessments confirmed that FT-Pep or TimP EVs were systemically inert, with serum pro-inflammatory markers and liver enzymes remaining within baseline physiological ranges. Exploiting these beneficial effects, we engineered polymyxin B (PMB)@TimP EVs, which exhibited enhanced bactericidal activity, improved pH stability, and negligible mammalian cytotoxicity compared with free PMB. In a murine sepsis model, PMB@TimP EVs demonstrated clear in vivo efficacy at an equivalent dose, maintaining survival when free PMB failed. Collectively, this study identified TimP as a conserved target and demonstrated a Trojan-horse drug delivery system capable of restoring the efficacy of PM against MDR gram-negative pathogens.