Abstract:

This paper describes the in vitro anti-Aeromonas hydrophila effect of the purified lipopeptide produced during the fermentation of Bacillus subtilis fmbJ. The inhibition zone method was adopted for the determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The antibacterial activity of lipopeptide was also evaluated based on the influences on the morphosis and membrane permeability of Aeromonas hydrophila. The results showed that Aeromonas hydrophila was sensitive to the lipopeptide, with 20 μg/mL MIC and 32 μg/mL MBC. The lipopeptide induced the cell membrane permeabilty of Aeromonas hydrophila, which caused the death of cells for the leakage of intro-cellular ions, proteins and nucleic acids. Further observations under scanning electron microscope (SEM) and transmission electron microscope (TEM) indicated that the lipopeptide led to the lack of cell wall, flagella lost and unclear intra-cellar components in Aeromonas hydrophil. As a result of effective antibacterial activity, the tested lipopeptide could be applied in prevention and control of aquatic animal diseases caused by Aeromonas hydrophila infection.

Key words: antimicrobial lipopeptide, Aeromonas hydrophila, minimal inhibitory concentration, minimum bactericidal concentration