Study On The Diversity Of The Intestinal Flora Of Sebastodes Schlegeli Under Different Culture Densities And Patterns

Intestinal flora can stimulate the proliferation of epithelial cells,accelerate nutrient absorption and metabolism and natural immunity,which can provide important reference indicators for animal health management.As an important economic fish species in the north,it is important to study its intestinal flora.The present study was conducted on six-month-old Sebastes schlegelii.A preliminary analysis of the intestinal flora and the microbial diversity and potential functions of the culture water at different culture densities,different culture modes and different growth and development stages of the Sebastes schlegelii was conducted by 16S r DNA high-throughput sequencing technology,and the results were as follows:1.A comparative analysis of the structure and function of the gut and culture water flora of the Sebastes schlegelii at three culture densities,low（3.81 kg/m³）,medium（5.09 kg/m³）and high（7.59 kg/m³）,was conducted.At the phylum and genus levels,the composition of the gut and culture water flora was the same for the three culture densities,but the abundance was different.Alpha diversity was significantly higher in the low-density gut than in the medium-density and high-density gut groups（p<0.05）,and the abundance of the Actinobacteria,Verrucomicrobiota and Acidobacteria decreased with increasing culture density.Further analysis by PCo A and Anova showed that nine genera were significantly higher in high-density water than in low and medium-density water（p<0.05）;RDA correlation analysis showed that high-density water was more affected by NH₄⁺-N and NO₂^--N,and the abundance of Vibrio,Pseudoalteromonas and Photobacterium were positively correlated with NH₄⁺-N and NO₂^--N,while the abundance of Flavobacterium,Fibrobacter and Vibrio was negatively correlated.In addition,the intestinal flora functions of the Sebastes schlegelii were mainly global and summary maps,carbohydrate metabolism and amino acid metabolism.Phenotypic prediction analysis yielded high levels of anaerobic and Gram-positive bacteria in the gut,mainly in the Firmicutes,and high levels of aerobic bacteria in the water,mainly in the Bacteroides.2.The composition and functions of the intestinal and aquaculture water flora of Sebastes schlegelii under the recirculating water culture and running water culture modes were compared and analysed.The results showed that the dominant intestinal flora in both modes were mainly Muribaculaceae,Desulfovibrionaceae,Lachnospiraceae,etc.The first dominant genera in the water in both the recirculating water and flow-through culture modes were Pseudoalteromonas,and the abundance of Thalassotalea and Polaribacter were twice as abundant in the water column as in the recirculating water column,while Flavobacterium and NS3a＿marine＿group were almost exclusively present in the recirculating water column.Clostridia,Trichoderma and Desulfovibrio were significantly more abundant in the gut than in flowing water（p<0.05）,and Flavobacterium and Vibrio were significantly more abundant in the aquaculture water（p<0.05）.The Firmicutes and the Bacteroides were significantly higher in the gut of flow-through culture than in recirculating water culture（p<0.05）,and the Enterobacteraies and Pseudoalteromonas were significantly higher in the culture water than in the recirculating water culture model（p<0.05）.The recirculating water culture model was aerobic,and the Gram-negative phenotypes of Alternomonas and Flavobacterium were higher than in the flow-through culture.3.A study on the composition and functional characteristics of the intestinal and culture water flora of Sebastes schlegelii at different growth stages found that the Alpha diversity was significantly higher in the culture water at 6 months than at September and 21 months（p>0.05）.the Helicobacter,Candidatus＿Bacilloplasma and ASF356 strains were significantly higher in the intestinal tract of Sebastes schlegelii at 6 months of age than at 9 and 21 months of age（p<0.05）and Marivivens was significantly higher at 21 months of age than at 6 and 9 months of age（p<0.05）.The Microtrichaceae,Gemmataceae,Flavobacteria,Enterobacteriaceae,Roseovarius,Pseudomonas,Nitrospirillum and Nitrospirillum were significantly higher at 6 months of age than at 9 and 21 months of age（p<0.05）.Rhodospirillales,Marineomonas,Cobetia and Celeribacter were significantly present at 9 months of age（p<0.05）.Polaribacter and Dasania were significantly higher（p<0.05）than the previous two stages at 21 months of age.Functional prediction analysis revealed that heterologous biometabolism and degradation,lipid metabolism,signal transduction,cell community-prokaryotic and amino acid metabolism were significantly higher in the intestinal flora at 9 months of age than at 6 months of age.It was concluded that the intestinal flora of Sebastes schlegelii showed dynamic changes at different stages,and that these changes may help the host to adapt to a complex and changing life history.In addition,the intestinal flora diversity was higher and more beneficial bacteria were present in the flow-through culture modesl and medium density group.The data of this study provide a theoretical basis for the healthy cultivation of Sebastes schlegelii.In summary,this study is the first to elucidate the composition and functional characteristics of the intestinal flora of Sebastes schlegelii under different culture densities,patterns and growth stages.This study will provide a data base for the healthy culture and development of probiotics for the Sebastes schlegelii,and promote the healthy development of the aquaculture industry in China.