Research On The Dynamics Of The Intestinal Microbes Of The Saker Falcon

In recent years,the research on the intestinal microbes of animals has been an international hot spot.Birds occupy an important position in the ecological system.But that research of bird intestinal microbes,especially raptors,has not been carried out extensively.Our experiment studied intestinal microbes and their adaptive evolution of carnivorous birds including saker falcons(Falco cherrug)and other falcons,owls,some herbivorous and omnivorous birds by high throughput 16S rRNA sequencing and metagenomic prediction.The distribution of the samples involves Mongolia,Qinghai and Sichuan Province in China,Beijing Zoo,IFAW Beijing Raptor Rescue Center and Beijing Xiaolongmen Forest Park.Finally,we got 243 tubes of intestine samples and 183 tubes of faeces including 14 species of raptor and 30 species of other birds.In total,9299786 effective sequences were obtained,and 437393 OTUs were defined.Adult sakers have significant differences in intestinal microbial composition and diversity compared with chicks.The results of identification showed that in saker's intestine,the most abundant bacteria were Proteobacteria(66.39%)and Firmicutes(24.61%).Other bacteria including Actinobacteria(3.70%),Cyanobacteria(2.28%),Tenericutes(0.20%)and Bacteroidetes(0.19%)also existed in the gut.However,in the chicks,the most abundant bacteria were Firmicutes(42.28%),Proteobacteria(37.35%),Bacteroidetes(5.74%),Chloroflexi(2.31%).Among them,the relative abundance of Firmicutes,Bacteroidetes,Chloroflexi are all significantly higher than adults'(P<0.05)while abundance of Proteobacteria is much lower than adults'(P<0.001).Composition of adults' intestinal microbes differed from that of chicks,which is more evener than adults'.In addition,the degree of chicks' intestinal microbial diversity and richness were significantly higher than adults'.After the birth of animals,the colonization of microbes occurs in the animals' intestine.At the early stage of colonization,microbes from diet and environment are transplanted to intestine,which makes the composition unstable.Moreover,the colonization of a large amount of microbes makes the intestinal microbes keep a high diversity and richness.Along with the time,selection would occur in the sakers' intestine and Proteobacteria would be enriched.After that,the diversity and richness decreased a lot.Metagenomics analysis reaveled that the pathways including energy metabolism,carbohydrant degradation,and transcription factors were enriched to cope with the rapid growth of chicks,which also lead to the demand of diverse and rich microbes.Birds under different diets have divergent intestinal microbes.In all our samples,the most abundant bacteria in birds is Proteobacteria,and after that is Firmicutes,which is most abundant in mammals' intestine.(1)Birds under different diets have different microbial composition.The relative abundance of Bacteroidetes in herbivorous birds is significantly higher than birds under other diets(P<0.01).(2)The cluster analyses of PCoA and UPGMA tree reaveled that the divergent intestinal microbes were caused by the different diets.The samples from carnivorous birds were clustered as one branch,and samples from other diets were clustered as the other branch.(3)In this article,saker,buzzard(Buteo hemilasius)and budgerigar(Melopsittacus undulatus)were selected as saker and budgerigar are close in host phylogeny while owning total different diets.Buzzard,owns a similar diet while far from saker in host phylogeny.The result showed that samples from saker and buzzard clustered while samples from budgerigar were far from them.The results indicate that diet of hosts has a great impact on the composition of intestinal microbes.Diet can influence the composition of intestinal microbes.Birds of different diet have different composition of intestinal bacteria.The proportion of Bacteroidetes in herbivore birds is much higher than carnivorous and omnivorous birds(P<0.01),because Bacteroidetes can ferment carbohydrate in plants and herbivore birds consume a lot of plants which they can't digest by themselves.As we know,the diversity and richness among the intestinal microbes in mammals with different diets are different.Among birds,the diversity and richness of bacteria in intestine differ from the birds with another diet.The diversity and richness of the intestinal in birds increases from carnivorous birds to omnivorous birds to herbivorous birds.The high diversity and richness of herbivorous birds' intestinal microbes are caused by the indigestible plant carbohydrate and protein intaken.The metagenomics analysis revealed that function of birds under different diets intestinal microbes diverged.The microbes in herbivorous birds help digest the indigestible plant the herbivorous birds consumed,so the proportion of pathway in coding peptidase and fermentation of carbohydrate enriched.In addition,due to the lack of protein and amino acid consumed,microbes involve in more biosynthesis of amino acid and protein export pathways than carnivorous birds and omnivorous birds.By this,microbes help the herbivorous hosts adapt to their diet.The function of different intestine parts differs and microbes in the different parts,especially the hindgut of birds.While the foregut is the main organ of absorption,the microbes in foregut have higher proportion of coding transporters,which help absorb nutrients from food intaken.