The Screening Of Antagonistic Bacteria Of Hydrophila Aeromonas And The Study Of Antagonistic Properties From Megalobrama Amblycephala

This study used the method of disk diffusion to isolation and screen antagonistic bacteria, and screened excellent biological control strains and determined its biological taxonomic status. This study investigated the biological safety of biocontrol strains, and test the antagonism and detect the protect in fish. Obtained the following conclusions:1. With the method of disk diffusion, the initial separation of131monoclonal strains sparated in LB medium, TCBS medium and MacConkey medium were screened.15bacteria antagonism with pathogenic Aeromonas hydrophila were filtered out.2. In vitro, five antagonistic bacteria were screened by the determination of antibacterial spectrum, co-agglutination rate and the co-culture conditions with pathogenic Aeromonas hydrophila. They were named as S13, S18, S24, S25and F4. The antagonistic bacteria S18, S24and F4indicators are good in all respects. They can be further developed as potential probiotics.3. Experiments on morphological characteristics, physiological characteristics and the16SrRNA, gyrB sequencing analysis of S18, S24and F4were conducted. The results identified that they are Bacillus amyloliquefaciens.4. In vivo, toxicity test showed antagonistic bacteria S24is safe to the Megalobrama amblycephala, does not produce toxicity. The protective immunity tests found that, the Megalobrama amblycephala obtain the immune protection rate of60%when the concentration of antagonistic bacteria S24is to107CFU/kg in the feed. The antagonistic test of Aeromonas hydroohila marked with green fluorescent protein gene showed that the antibacterial effect is consistent with the vitro. In summary, as the biocontrol antagonists of Aeromonas hydrophila, antagonistic bacteria S18, S24and F4have significant and safe control effect. Research on antagonism, safety, and protection force indicated that antagonistic bacteria S24were effective, security and has the potential of commercial application. This research lay a good foundation of prevention and control of aquatic diseases.