Bacterial Community Assembly And Turnover Within The Intestines Of Japanese Flounder (Paralichthys Olivaceus) During Early Life Stages

In this paper,we study the changes of intestinal microflora and the regularity of colonization of Paralichthys olivaceus.The aim of this study was to provide a mechanism for the formation of intestinal flora in order to achieve the healthy scale of flounder and control technology aspects of theoretical basis.The main findings are as follows:1.Illumina MiSeq of 16 S rRNA and biological information analysis method were used to explore the intestinal bacterial community composition in indoor tank-culture system.Sampling was carried out throughout the larvae and juvenile stages for six time points.The obtained 7462 operational taxonomic units(OTUs)were classified into 42 bacterial species and 972 genera.The relative abundance of Proteobacteria,Firmicutes and Bacteroidetes were 55.20%,13.37% and 21.58%,respectively of the 1 day-post-hatch(dph).h G2(> 90%)Proteobacteria became the absolute dominant flora of the intestinal at 9 dp.After 45 dph,the relative abundance of the mycobacterium was significantly decreased and the thickness of the strain was significantly lower The relative abundance of Vibrio was the highest during the period of alive feed(9 and 21 dph),and was the lowest level after feeding formulated feed(115 dph).By contrast,the Bacteroides and Prevotella became the predominant intestinal bacteria at 80 dph,whereas Firmicutes became a core microbiota at 80 dph.Blautia and other related genus colonized in the intestinal of flounder and became the dominant microbiota between 80 and 115 dph.2.The relative abundance of Proteobacteria(78.21%)and Bacteroidetes(13.33%)in Rotifer,while the content of Vibrio was very low(0.77%).The dominant phylum of Artemia were Proteobacteria,Bacteroidetes and Firmicutes,their OTUs were greater than 98.26%,and the dominant gunus was Vibrio(28.34%)There were significant differences between the dominant genus of rotifer and Artemia.There were 12 dominant guenus in compound food(F4),mostly of B Firmicutes,including Lactococcus and Staphylococcus.The dominant genus in the F5 compound food are Schwanella,Psychrobacter and Acinetobacter,which are different from those of F4.The relative abundance of Cyanobacteriumwas 74%,becoming the predominant phylum.The results showed that the phylum in the water samples were not changed Significantly,,but the dominant genus had obvious change.1 dph W1 samples were rich in diversity of bacteria,there are 14 dominant genus,Proteobacteria is the predominant bacteria of 9 dph W2 samples,Flavobacteria(Flavobacteriales)relative abundance increased to 32.4%.The relative abundance of Vibrio and Pseudomonas was 20.7% and 13.7%,respectively.The relative abundance of Flavobacterium in the 45 dph W4 sample was about 17.34%,and the relative abundance of the Pseudomonas was 38.94%,and the numbers of dominant genus in the 80 dph water W5 decreased;In 115 dph W6 Lactococcus increased to become dominant bacteria,and composition of bacterial is similar to W5.3.The similarity analysis of diets,water and intestinal sample flora in six sampling stages.The similarity of intestinal flora and diets was 17.61% and 41.11%,respectively during feeding alive food.After the conversion of the compound feed,the intestinal flora was similar to the flora of the feed decreased gradually,at 115 dph,the similarity was only 3.34%,and the common dominant genus disappeared.The similarity of the Yolk sac larvae and the water was 26.77%,and the number of dominant genus were 3.The similarity between the intestinal flora and the water was about 7% after feeding.At 115 dph,the similarity of water bodies was reduced to 1.15%,and there was no common dominant genus.The results showed that the correlation between intestinal flora and diets(Spearman correlation Rho 0.588,P <0.05)was much higher than that between intestinal flora and water(Spearman correlation Rho 0.15,P & lt;0.5).4.After the gut of flounder was opened,the intestinal flora had obvious succession,and the numbers and quantity of intestinal microflora had significant changes.The relative abundance of Vibrio was the highest in the intestine,and the relative abundance of the Proteobacteria decreased gradually at 45 dph,and the abundance of Firmicutes and Bacteroidetes was increased.And the genus Bordetella became the dominant bacteria at 80 dph.The strains of the thick-walled bacteria There were eight dominant genus in the juvenile fish belonging Firmicutes,the intestinal flora structure was similar to the adult fish which feeded in farm The results of the study revealed the structure and succession of intestinal flora in larvae,juvenile and young flounder under the breeding.