Isolation,Identification Of Pathogenic,Antagonistic Bacteria Of Strawberry And Preliminary Study On Antimicrobial Properties

The occurrence of postharvest diseases of strawberry is mainly caused by the invasion of pathogenic microorganisms. The use of chemical fungicides to protect postharvest fruits had been considered as the most effective method. But there are many disadvantages, such as the harm to human health, the environment pollution and the resistance of pathogenic bacteria. It is imperative to use nontoxic and harmless fresh keeping method to replace the use of chemical fungicides. Among these, biological control using harmless antagonistic microorganisms was proved to be a promising strategy for managing fruit diseases.In this study, a pathogenic bacterium was isolated from rotting strawberries. The pathogenic bacteria was identified by morphology and molecular biology. Then, the antagonist bacterium with stronger antibiotic effect against pathogenic bacteria was selected.By morphological, physiological and biochemical identification, molecular biology identification, this strain was identified. The best inhibitory condition of antagonistic bacteria was studied. Extract the antibacterial substances of antagonistic bacteria. The main results and conclusions were as follows:1. Isolation and identification of pathogenic bacteria: The strain A1 had been collected and analyzed from the rot strawberries and had highly homologous with Alternaria alternata by phylogenetic tree analysis. The strain A1 was preserved in Agricultural Microbiological Collection Center and the number was AMCC 300095.2. Screening and identification of antagonistic bacteria: 15 strains with stronger antibiotic effect against strawberry Alternaria alternata were selected by adopting plate stand-opposite culture method. By observing the morphology characteristics and analyzing the 18 S rDNA sequences, the strain C7 and C19 were identified as Brevibacillus laterosporu. The growth curve of strains tured the delayed phase into the logarithmic phase at4 h and tured into stationary phase at 14 h.3. Conditions for the antimicrobial activity of Brevibacillus laterosporu C19: The strain C19 got the best antibacterial effect at 30 ℃ pH = 7 after 96 h fermentation.4. Antibacterial properties of Brevibacillus laterosporu C19: In vivo experiment, the fermentation supernatant of Brevibacillus laterosporu C19 had the best antibacterial activity.And the 80% precipitation of ammonium sulfate saturation of the material had the best antibacterial activity.