Pecbloodin _18-37 : a promising antimicrobial peptide from <i>Boleophthalmus pectinirostris</i> with therapeutic potential against <i>Edwardsiella tarda</i> infection

<i>Edwardsiella tarda</i> is a significant pathogen in aquaculture, causing severe systemic infections and considerable economic losses worldwide. The limited efficacy of current treatments and the emergence of multidrug-resistant strains underscore the urgent need for novel antimicrobial strategies. Antimicrobial peptides have garnered increasing interest due to their broad-spectrum activity and low risk of resistance development. In this study, we identified a novel immune-related gene from the mudskipper <i>Boleophthalmus pectinirostris</i>, named <i>Pecbloodin</i>, which encodes a mature peptide of 67 amino acids. A truncated peptide derived from this sequence, Pecbloodin_18-37, exhibited broad-spectrum antibacterial activity, high thermal stability, and tolerance to sodium ions. Functional assays demonstrated that Pecbloodin_18-37 exerts rapid bactericidal effects by compromising bacterial membrane integrity, inducing cellular content leakage, and triggering endogenous reactive oxygen species accumulation. Furthermore, it effectively inhibited bacterial biofilm formation and did not promote resistance under prolonged exposure. Importantly, <i>in vivo</i> experiments using an <i>E. tarda</i>-infected mudskipper model revealed that Pecbloodin_18-37 significantly improved host survival and modulated the immune response. Overall, Pecbloodin_18-37 shows great potential as a promising alternative to conventional antibiotics for the control of <i>E. tarda</i> infections in aquaculture, addressing the pressing issue of antibiotic resistance.IMPORTANCE<i>Edwardsiella tarda</i> is an urgent threat to global aquaculture. We mined the mudskipper <i>Boleophthalmus pectinirostris</i> genome for antimicrobial peptide and identified Pecbloodin_18-37, a 20-aa thermostable peptide that rapidly permeabilizes bacterial membranes, elicits intracellular reactive oxygen species, blocks biofilm formation, and does not select for resistance. In <i>E. tarda</i>-challenged fish, a single dose reduced mortality by 25% and restored immune homeostasis. The peptide is readily synthesized and feed-compatible, providing an immediate, resistance-proof substitute for conventional antibiotics in fish farming.