Probiotic Potential of Enterococcus lactis GL3 Strain Isolated from Honeybee (Apis mellifera L.) Larvae: Insights into Its Antimicrobial Activity Against Paenibacillus larvae

This study aimed to address the need for effective probiotics and antibacterial agents to combat American foulbrood disease in honeybees, caused by <i>Paenibacillus larvae</i>. In the context of declining honeybee populations due to pathogens, we isolated eight lactic acid bacteria (LAB) strains from honeybee larvae (<i>Apis mellifera</i> L.) and evaluated their probiotic potential and inhibitory effects against <i>P. larvae</i>. Methods included probiotic property assessments, such as acid and bile salt resistance, hydrophobicity, auto-aggregation, co-aggregation with <i>P. larvae</i>, antioxidant capacities, osmotolerance to 50% sucrose, and antibiotic susceptibility. Results indicated that the GL3 strain exhibited superior probiotic attributes and potent inhibitory effects on <i>P. larvae</i>. Whole-genome sequencing revealed GL3 to be an <i>Enterococcus lactis</i> strain with genetic features tailored to the honeybee larval gut environment. Pangenome analysis highlighted genetic diversity among <i>E. lactis</i> strains, while molecular docking analysis identified aborycin, a lasso peptide produced by GL3, as a promising inhibitor of bacterial cell wall synthesis. These findings suggested that GL3 was a promising probiotic candidate and antibacterial agent for honeybee health management, warranting further investigation into its in vivo efficacy and potential applications in beekeeping practices.