Journal Article

The Marine Antimicrobial Peptide AOD with Intact Disulfide Bonds Has Remarkable Antibacterial and Anti-Biofilm Activity

Yang, Na, Wang, Jianhua, Li, Yuanyuan, Hao, Ya, Mao, Ruoyu, Teng, Da, Gu, Xinxi, Lu, Haiqiang, Zhao, Qingyi

2024

Overview

American Oyster Defensin (AOD) is a marine peptide that is derived from North American mussels. It has been demonstrated to exhibit potent antimicrobial activity and high safety in both in vitro and in vivo models. In this study, to facilitate synthesis, mutants of AOD with fewer disulfide bonds were designed and subjected to structural, antimicrobial, and anti-biofilm analysis. The antimicrobial activity of AOD-derived peptides decreased after reduction in the disulfide bond, and among its three derivatives, only AOD-1 inhibited very few bacteria with a MIC value of 64 μg/mL, whereas the others had no inhibitory effect on pathogenic bacteria. The findings demonstrated that full disulfide bonds are indispensable for bactericidal activity, with the α-helix playing a pivotal role in inhibiting bacterial membranes. Furthermore, the results of the ATP, ROS, membrane potential, and membrane fluidity assays demonstrated that intracellular ATP, reactive oxygen species, and membrane fluidity were all increased, while membrane potential was reduced. This indicated that AOD resulted in the impairment of membrane fluidity and induced metabolic disorders, ultimately leading to bacterial death. The inhibitory effect of AOD on the biofilm of S. epidermidis G-81 was determined through the crystal violet and confocal microscopy. The results demonstrated that AOD exhibited a notable inhibitory impact on the biofilm of S. epidermidis G-81. The minimum biofilm inhibitory concentration of AOD on S. epidermidis G-81 was 16 μg/mL, and the minimum biofilm scavenging concentration was 32 μg/mL, which exhibited superior efficacy compared to that of lincomycin. The inhibitory effect on the primary biofilm was 90.3%, and that on the mature biofilm was 82.85%, with a dose-dependent inhibition effect. Concurrently, AOD cleared intra-biofilm organisms and reduced the number of biofilm-holding bacteria by six orders of magnitude. These data indicate that disulfide bonds are essential to the structure and activity of AOD, and AOD may potentially become an effective dual-action antimicrobial and anti-biofilm agent.

• Publisher: MDPI AG,MDPI
• Subject: American Oyster Defensin (AOD) / Amino acids / Animals / Anti-Bacterial Agents - chemistry / Anti-Bacterial Agents - pharmacology / anti-biofilm activity / Anti-infective agents / Antibiotics / Antiinfectives and antibacterials / Antimicrobial activity / Antimicrobial peptides / Antimicrobial Peptides - chemistry / Antimicrobial Peptides - pharmacology / ATP / Bacteria / Bactericidal activity / Biofilms / Biofilms - drug effects / Bonding agents / Chemical bonds / Confocal microscopy / Control / Defensins / Defensins - chemistry / Defensins - pharmacology / Disease resistance / disulfide bond / Disulfide bonds / Disulfides - chemistry / Disulfides - pharmacology / Drug resistance / Effectiveness / Environmental aspects / Fluidity / Gentian violet / Gram-positive bacteria / In vivo methods and tests / Infections / Lincomycin / Marine molluscs / Membrane fluidity / Membrane potential / Membranes / Metabolic disorders / Microbial mats / Microbial Sensitivity Tests / Microscopy / Mussels / Ostreidae / Pathogenic bacteria / Pathogens / Peptides / Physiological aspects / Reactive oxygen species / Scavenging / Shellfish / Spectrum analysis / Staphylococcus epidermidis / Staphylococcus epidermidis - drug effects / Testing