| The deterioration of the aquaculture environment and disease often outbreaks under the high density pond culture mode of fish, probiotic/probiotics is the main and efficient method to regulate microbiota of fish intestinal tract and pond water environment, which will improve the aquaculture condition and reduce the incidence of diseases. To investigate the effects of probiotics on composition and diversity of microbiota in intestinal tract and pond culture environment of Japanese flounder (Paralichthys olivaceus), samples from Japanese flounder intestinal tract as well as environmental factors (culture water, feed and pond sediment) were collected. High throughput sequencing of 16S rDNA gene was employed to analyze the regulation of probiotics on microbiota of intestinal tract and environmental samples. Our results showed that the diversity of microbiota in pond sediment and intestinal tract of Japanese flounder were increased after adding the probiotics. Moreover, the diversity of microbiota in pond sediment was still the highest. Inversely, the diversity of microbiota in culture water was declined, which was lower than that in the intestinal tract. Firmicutes, Proteobacteria and Fusobacteria were dominant in Japanese flounder intestinal tract, after the addition of probiotics, relative abundances of Firmicutes and Proteobacteria increased while Fusobacteria decreased. At the genus level, relative abundances of Enterobacter and Bacillus increased while Acinetobacter and Photobacterium firstly increased and then decreased in Japanese flounder intestinal tract with the conduct of this experiment. Relative abundances of Chloroplast_norank increased from 42.39% to 61.44% in culture water of Japanese flounder. In pond sediment, the change of relative abundance of Bacillus was obvious, rising from 3.78% to 33.64%. Relative abundances of Vibrio in fish intestinal tract, culture water and pond sediment decreased after probiotics were added. Some strains of Acinetobacter and Vibrio are important pathogens in aquaculture. The microbiota structure in intestinal tract of Japanese flounder was more similar to that in pond sediment. Changes of these main microbiota relative abundances indicated that the addition of probiotics could optimize the microbiota structure of Japanese flounder intestinal tract and environment. However, it is impossible that Lactobacillus as the main microbiota of probiotics was able to colonize and persist in the fish intestinal tract, water and pond sediment, which indicated that probiotics deliver not the bacteria but their probiotic function. Hence, the addition of probiotics could affect the microbiota structure of Japanese flounder intestinal tract, water environment and pond sediment. |
