A novel antimicrobial peptide Anguinin55-72 identified from Anguilla japonica exhibiting protection against Edwardsiella tarda infection.

Edwardsiella tarda poses a substantial threat to fish populations, inducing severe systemic infections, especially pronounced in economically valuable species such as the Japanese eel (Anguilla japonica). Current therapeutic options are limited, and the emergence of multidrug-resistant strains further underscores the urgent need to develop novel antimicrobial alternatives. Antimicrobial peptides present promising alternatives because of their extensive activity range and minimal potential for resistance development. In this study, we identified a novel functional gene from A. japonica, named Anguinin, which encodes a mature peptide comprising 99 amino acids. The Anguinin gene was broadly expressed in various tissues of healthy A. japonica and showed significant induction in immune-related tissues following E. tarda infection. A truncated peptide, Anguinin55-72, derived from this gene, exhibited potent antimicrobial properties against a wide range of pathogens. Mechanistic studies revealed that Anguinin55-72 disrupted bacterial membranes, increased membrane permeability, and triggered the accumulation of reactive oxygen species, ultimately causing bacterial death. The peptide also demonstrated anti-biofilm activity and maintained stability at high temperatures without cytotoxicity. The in vivo animal models were constructed using zebrafish and Japanese eels infected with E. tarda. The results showed that Anguinin55-72 significantly increased survival rates of Danio rerio and A. japonica. Additionally, in the Japanese eel model, Anguinin55-72 significantly reduced disease severity, decreased bacterial loads, downregulated the expression of pro-inflammatory cytokines and promoted the recovery of tissue lesions. Taken together, Anguinin55-72 holds promise as an alternative to conventional antibiotics for controlling E. tarda infections in aquaculture to address the challenge of escalating antibiotic resistance.