Taxonomic And Functional Metagenomic Profiling Of Gastrointestinal Tract Microbiome Of The Whooper Swan (Cygnus Cygnus)

The Whooper Swan is a typical long-distance migratory bird which mainly inhabits coastal wetlands or lakes.The migratory nature of the Whooper Swan has an extremely complex life history,with long-distance round-trip flights between breeding areas,migratory areas and wintering areas almost every year.Complex habitats and different selection pressures may lead to complex and diverse microbial composition of the gastrointestinal tract,and therefore it is an ideal research object for animal gastrointestinal tract microbiome.In this study,the feces of two typical wintering grounds of the Whooper Swan in Rongcheng,Shandong and Sanmenxia,Henan,northern China were studied,and the diversity,structure and function of the gastrointestinal tract microbiome were carried out by using metagenomic sequencing technology.Compare systematic research,and compared with the gastrointestinal tract microbiome of the geese,chickens,domestic geese and black-tailed gulls,the differences in the structure of the microbiome between different animals were analyzed,and the differences were initially identified.In the study,we found that the dominant bacteria in the microbes of the swan feces mainly included Firmicutes(41.1%)?Proteobacteria(22.9%)?Cyanobacteria(11.5%)?Bacteroidetes(8.7%)?Fusobacteria(6.6%)?Actinobacteria(5.6%.By comparing the samples from Rongcheng and Sanmenxia,we found that the average content of Firmicutes bacteria in the fecal samples of Rongcheng Whooper Swan was 32%,while the average content of Firmicutes bacteria in the Sanmenxia sample was as high as 78%.However,by comparing the gastrointestinal tract microbiome of the swans and habitat soils and water samples,we found that the structure of the gastrointestinal tract microbiome of the Whooper Swan was significantly different from that of the environment,and it could be speculated that the habitat of the host did not cause gastrointestinal tract microbiome.The gastrointestinal tract microbiome was different and this difference was more likely to be related to diet.In addition,cyanobacteria were widely found in Rongcheng's Whooper Swan samples.However,the samples of chickens,ducks,greylag and geese collected in Beiliu Village in this area were extremely low,and some samples were not detected.At the same time,the content of cyanobacteria in the feces samples of the Whooper Swan collected by Sanmenxia was extremely low,and some samples were not detected.The shallow seawater inhabited by Rongcheng's swan was rich in cyanobacteria.Therefore,we speculate that Cyanobacteria entereds the body due to feeding and eventually appeared in the discharged feces.In addition,by comparing with the water in the habitat and the flora in the soil,it was obvious that the composition of the intestinal flora of the bird was significantly different from the composition of the flora in the water and soil,such as Firmicutes bacteria.The content of the door in the environmental samples(soil and seawater)was significantly less than that of the feces,so environmental microbes had little effect on the diversity and composition of the intestinal bacteria.By comparing the intestinal flora of geese,chickens,domestic geese,and black-tailed gulls,we found that the gastrointestinal flora of the Whooper Swan was different from such species at different levels of classification.In summary,although the formation of the gastrointestinal flora of the Whooper Swan was affected by many factors,its phylogenetic status and feeding habits were two important factors affecting the composition of the gastrointestinal flora.The formation of intestinal flora has a more important role.In this study,preliminary functional annotations of the macro-genome of the swan fecal flora were carried out.After comparison with other animals,the potential functions of the intestinal flora were analyzed in combination with the physiological and ecological characteristics of the swan.The Whooper Swan mainly feeds on algae and plants.Animals that use plants as their main food source need 60%of the cell wall-like components of cellulose,hemicellulose,etc.which are difficult to digest and absorb.The bacteria capable of degrading polysaccharides such as cellulose mainly include:Clostridium in the Firmicutes bacteria,Prevotella in the Bacteroides,and Spirulina.The results of this study at the "Order" level show that Clostridium was the most dominant flora,so we speculate that the Clostridium in the Firmicutes bacteria could better help the Whooper Swan adapt to the food rich in crude fiber.And the Firmicutes bacteria could produce a lot of short-chain fatty acids,which promote the body's absorption and gain energy.Furthermore,metabolic pathway studies(such as KEEG analysis)had also found that the swan gastrointestinal tract flora was involved in fatty acid metabolism,Carbohydrate metabolism,and Peptidase production.The physiological process of decomposition and absorption of herbivore showed that the Whooper Swan gastrointestinal tract flora was well adapted to its feeding habits.Other dominant bacteria such as Proteobacteria were also involved in plant digestion.Many species of Proteobacteria had important degradation effects in various food decomposition.The high abundance of Proteus in the gastrointestinal tract of the Whooper Swan might be complicated strategy for eating.Bacteroides was also the dominant flora in the gastrointestinal tract of the Whooper Swan.Bacteroides bacteria had the function of degrading carbohydrates and proteins,and could also complement the host's involvement in the degradation of resistant cellulose,pectin and xylan.In summary,the gastrointestinal tract microbiome played an extremely role which the Whooper Swan could adapt to its diversified diet structure,and the animal and its gastrointestinal tract microbiome were the coevolutionary relationships.A total of 738 "genus" microorganisms were identified in this study,including unclassified Clostridiaceae,unclassified Streptophyta,Turicibacter,Lactobacillus,and Fusobacterium.(Fusobacterium),Psychrobacter,Unclassified Ruminococcaceae,Bacteroides,Flavobacterium,Unclassi fied Moraxellaceae,Streptococcus Streptococcus,Cetobacterium.Common intestinal pathogens such as Escherichia coli and Salmonella in birds were not dominant bacteria in all tested individuals.Therefore,we believe that once the gastrointestinal tract flora was established in the adult gastrointestinal swan,its diversity and structural composition were highly stable;second,the rise of the swan tourism in recent years had led to the swan a frequently contact with human,poultry animals and other wild animals,but artificial feeding did not lead to the introduction of common pathogenic bacteria in humans and domestic animals.It could be seen that the symbionts formed by the Whooper Swan gastrointestinal tract microbes and hosts had their own unique defense processing system against pathogenic microorganisms.Therefore,the results of this study could provide theoretical guidance for the conservation of the Whooper Swan and the guidance of the local development of the Whooper Swan tourism economy.