The microbial flora present in the intestine of the fish plays an important role such as to break 25 down ingested foods, or the inhibition of the colonization of the fish intestine by pathogens. 26 Because only a small percentage of microorganisms in seawater and freshwater can be 27 cultured and cultivated in the laboratory, molecular techniques based on 16S rDNA 28 amplification have been developed to detect and identify culturable and nonculturable 29 bacteria. Many studies have combined traditional methods with molecular methods to provide 30 more detailed informations on microbial communities. The aim of this work was to evaluate 31 the microbiota of Salmo trutta fario intestine using PCR-Denaturing Gradient Gel 32 Electrophoresis (DGGE) to assess the influence of a diet on the population composition. 33 Reference strains were used for protocol optimisation and microorganism identification by 34 DGGE analysis. Bacillus, Kocuria, Lactobacillus, Morganella, Mycoplasma, Proteus, 35 Pseudomonas, Salmonella, Serratia, Yersinia, Citrobacter, Pediococcus, and Fusobacterium 36 were identified using this method at different day time point feeding. Cluster analyses of 37 DNA fingerprints of the intestinal microbial population revealed differences in the intestinal 38 microbial flora of fish fed different diets. Gram-negative bacteria such as Aeromonas, 39 Pseudomonas, Enterobacteriaceae dominate, though Gram-positive bacteria such as 40 Lactobacillus have also been found. Different diets initiated as early as the first stage of life 41 affect the composition of the intestinal microbiota of fish. 42
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