A novel cyclic antimicrobial peptide N1-7567 targets Campylobacter jejuni through membrane disruption and metabolic disruption.

Campylobacter jejuni (C. jejuni) is a prominent foodborne pathogen commonly associated with poultry, representing a potential concern for global public health. Here, we identified a novel cyclic antimicrobial peptide, N1-7567, encoded by a noncanonical small open reading frame (ORF) in a Bacillus licheniformis (B. licheniformis) isolate. N1-7567 (AFLKRFSCRLIRAGKYLSCLLQPAA) adopts a cyclic conformation formed by a disulfide bond between two cysteine residues. N1-7567 exhibited a minimum inhibitory concentration (MIC) against C. jejuni of 64 μg/mL. Studies revealed that N1-7567 associates with the bacterial membrane, disrupts bacterial membrane integrity, and subsequently penetrates into the cytoplasm. This process triggers nitric oxide (NO) release, reactive oxygen species (ROS) accumulation, adenosine triphosphate (ATP) leakage, and direct interaction with bacterial genomic DNA, collectively leading to bacterial growth inhibition. Notably, N1-7567 significantly reduced Galleria mellonella mortality. Together, these findings highlight N1-7567 as a promising candidate for controlling C. jejuni infection and transmission.