Molecular taxonomy of intestinal bacteria from freshwater fish and its application

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Intestinal bacteria of fish was investigated and the following results were obtained.1. Phylogeny of intestinal bacteria isolated from goldfish were examined based on 16S rDNA sequences and they were divided into eight clusters : Aeromonas hydrophiila, Aeromonas sp., Citrobacter freundii, Shewanella sp., Vibrio sp., Vagococcus sp. and Fusobacteria and CFB group.2. Similarly, intestinal bacteria from tilapia and grass carp were mainly classified into five clusters : Aeromonas veronii, Citrobacter freundii, Plesiomonas shigelloides, Fusobacteria and CFB group.3. Cotrary to this, intestinal tract from Japanese flounder and red seabream were mainly divided into three clusters : Vibrio fischeri, V. scophthalmi and V. carchiae.4. Bacterial populations in goldfish feces were analyzed with fluorescentl in situ hybridization method and it was found that goldfish harbors α-, β- and γ-Proteobacteria at high densities. Probes AER66 and BAC303 could detect Aeromonas and Bacteroides type A, respectively.5. Antibacterial abilities of intestinal bacteria from Japanese flounder were determined using 4 fish pathogens, and it was found that 1.7-24.3% of intestinal bacteria possess the activities.