Characteristics Of Intestinal Flora Of Silver Carp And Bighead Carp In Taihu Lake

Gut microbes play an important role in promoting host growth and development and healthy immunity,while the composition of gut microbial community structure is influenced by various factors such as host species,gut structure,feeding habits and surrounding environmental factors silver carp and bighead carp are two major species of freshwater aquaculture in China,which not only have high economic benefits,but also produce ecological benefits of controlling cyanobacterial blooms and improving water quality.The area of Taihu Lake is large,and there are different degrees of eutrophication in each lake area due to the influence of topography and surrounding urban industries.Taihu Lake also has experimental areas for cyanobacteria control in bighead carp and silver carp cages,and different stocking patterns and survival environments have important effects on aquatic animal gut microbes.Therefore,this study was conducted to investigate the community structure characteristics of silver carp and bighead carp from three aspects: environmental differences in lake areas,stocking patterns,and different areas of the gut,and the results of the study are as follows:1.Composition and functional analysis of intestinal microflora of silver carp and bighead carp in different lakesThis study investigated the microbial composition,diversity,community structure,and predictive function in guts of two economical filter-feeding fish species and surrounding water in an unfed aquaculture system.Ninety-four fish guts and eighteen water samples were collected from the hydrophyte-dominated and the algae-dominated regions in Taihu Lake were subjected to 16 S sequencing.Results showed that Proteobacteria and Cyanobacteria were the dominant bacteria in water and fish guts.The abundance of certain microbial taxa in fish guts varied by habitats and fish species.Microbial alpha diversity was higher in surrounding water than in fish guts and higher in silver carp guts than in bighead carp guts.Adonis and principal coordinate analysis(PCo A)illustrated significant divergences in microbial community structures between water and fish guts,between fish guts from different habitats,and between fish guts of different species.Habitats contributed more to the variance of intestinal flora than fish species.PICRUSt analysis showed significant differences in the enrichment of some metabolism-related pathways(KEGG-level 2)between fish guts and surrounding water.These findings improve our understanding of gut microbes of these two filter-feeding fish and clarify their associations with habitats and host species,providing a scientific theoretical basis for the healthful aquaculture of fish.2.Gut microbes community characteristics of silver carp and bighead carp inside and outside the cageTo investigate the differences in gut microbes community of silver carp and bighead carp underdifferent stocking patterns,31 samples of fish guts(11 of silver carp and 20 of bighead carp)and 6 samples of aquatic environment water were collected from insied the cage and outside the cage in Taihu Lake and were sequenced by 16 S r DNA.The dominant microbial phyla in the gut of two fish species were Firmicutes,Proteobacteria and,Cyanobacteria.The abundance of cyanobacteria in the guts of two fish species was higher insided the cage than outside the cage,while the abundance of Firmicutes was lower than outside the cage.Alpha diversity analysis showed that the microbial diversity of two fish species and water inside the cage was higher than that outside the cage.Beta diversity analysis showed that there were significant differences in intestinal microbial community structure of two fish two species between inside and outside the cage,and the difference of bighead carp was greater than silver carp.These findings indicated that cage stocking pattern had a greater effect on the gut microbes of silver carp than of bighead carp,and the silver carp and bighead carp reared in cage could ingest more cyanobacteria.3.Characteristics of intestinal microflora in different intestinal regions of silver carp and Bighead carp in TaihuIn this study,the 16 S r DNA technique was used to sequence 60 intestinal samples of silver carp and bighead carp collected from Taihu Lake.The results showed that proteobacteria and cyanobacteria were dominant in the foregut of silver carp,while Fusobacteria and cyanobacteria were dominant in midgut of silver carp,and the dominant bacteria in hindgut of silver carp mainly included Fusobacteria,Cyanobacteria,Firmicutes and Bacteroidetes.The dominant phyla of bighead carp foregut are mainly Cyanobacteria and Proteobacteria,and the main phyla of microorganisms in midgut and hindgut are Cyanobacteria,Proteobacteria,and Fusobacteria.The results of alpha diversity index analysis showed that the diversity of microflora in midgut of silver carp was higher than that in foregut and hindgut,but the diversity of microflora in hindgut was higher than that in foregut and midgut.The changes in intestinal microflora diversity and richness of bighead carp were similar to those in silver carp.In terms of functional prediction(KEGG-Level 2),the functions of midgut and hindgut of silver carp were similar,but the contribution was different,and the functions of midgut and foregut of bighead carp were more similar.NMDS analysis also proved that the similarity of midgut and hindgut of silver carp was higher,and the foregut and midgut of bighead carp were closer.These results improved our understanding of the intestinal microbe of silver carp and bighead carp,and nd the distribution of gut microbe of silver carp and bighead carp.