Bacillus amyloliquefaciens G1: A Potential Antagonistic Bacterium against Eel-Pathogenic Aeromonas hydrophila

Abstract

Recent studies have revealed that the use of probiotics is an alternative to control marine aeromonas. However, few probiotics are available against Aeromonas hydrophila infections in eels. In the present study, a potential antagonistic strain G1 against the eel-pathogenic A. hydrophila was isolated from sediment underlying brackish water. Its extracellular products with antibacterial activities were shown to be stable under wide range of pH, temperature, and proteinase K. It was initially identified as Bacillus amyloliquefaciens using API identification kits and confirmed to be B. amyloliquefaciens strain (GenBank accession number DQ422953) by phylogenetic analysis. In addition, it was shown to be safe for mammalians, had a wide anti-A. hydrophila spectrum, and exhibited significant effects on inhibiting the growth of the eel-pathogenic A. hydrophila both in vitro and in vivo. To the best of our knowledge, this is the first report on a promising antagonistic Bacillus amyloliquefaciens strain from brackish water sediment against eel-pathogenic A. hydrophila.

Figure 1

Phylogenetic tree constructed using neighbor-joining method.

Figure 2

Inhibitory effect of srain G1 at the final cell density of 10³ cfu/mL (A), 10⁴ cfu/mL (B), 10⁵ cfu/mL (C), and 0 cfu/mL (D) on the growth of the eel-pathogenic A. hydrophila.

Figure 3

Antagonistic spectrum of srain G1 against pathogenic A. hydrophila strains.

Figure 4

Protective effect of srain G1 on Anguilla anguilla (L.) under the eel-pathogenic A. hydrophila challenge trial.