Isolation, identification, and antibacterial characterization of Leuconostoc mesenteroides

Abstract:

[Background] Aquatic pathogenic bacteria threaten the health of aquatic organisms and restrict the development of aquaculture. The effective prevention and control of bacterial diseases in fish has become an urgent problem in aquaculture. [Objective] To screen out a bacterial strain with inhibitory effect on aquatic pathogenic bacteria, and to study its antibacterial properties and performance in controlling aquatic bacterial diseases. [Methods] The strain was identified after full consideration of the phylogenetic tree constructed based on the 16S rRNA gene and the physiological and biochemical characteristics. The antibacterial substances were extracted with ethyl acetate. The effects of the strain on the extracellular protease production and biofilm-forming ability of pathogenic bacteria were determined by azo casein method and crystal violet staining, respectively. Furthermore, the inhibitory effect of the strain on Aeromonas veronii Z12 was evaluated by animal experiment. [Results] The lactic acid bacterial strain DH was screened out from the fermented product of pickle and identified as Leuconostoc mesenteroides. The strain secreted extracellular antimicrobial substances, and showed antibacterial effect on Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, Aeromonas salmonicida, Shewanella putrefaciens, and A. veronii. The antibacterial substances could be extracted with ethyl acetate and had thermal stability. Strain DH inhibited the extracellular protease production and biofilm-forming ability of the tested pathogenic bacteria, and exhibited protection against the challenge of Aeromonas veronii Z12. [Conclusion] L. mesenteroides DH can inhibit the growth of aquatic pathogenic bacteria by secreting antibacterial substances, which has the potential for the prevention and control of bacterial diseases in fish.

Key words:aquatic pathogenic bacteria;Leuconostoc mesenteroides;antibacterial substances;protease production;biofilm-forming ability