Change Of Gut Microbiota In Microhyla Fissipes And Andrias Davidianus Through Metamorphosis

Amphibian plays an important role in the ecological system,which is a key transition group from aquatic to terrestrial animals.Up to date,most of researches on intestinal microflora of amphibian have not been researched and focused a lot.In this paper,Microhyla fissipes and Andrias davidianus was on behalf of the Anura and urodele respectively,and we presented dynamic change process of intestinal microbial group of amphibian through metamorphosis.Our study may supply some basic information of gut microbiomes for the data in vertebrate and uncover the secret of microbiota that were resident in the digestive tract and the relationship between host and microbiomes in co-evolution.Furthermore,research of microbial ecology in amphibian will provide more new idea for protection in the following days.The composition and diversity of intestinal microorganism were proved to be obviously dissimilar in the complex life of Microhyla fissipes,and metabolic pathway that involved are differentiated especially for ontogeny and change of diet from to herbivorous to carnivorous.We obtained 1423725 high quality sequences by 16S rRNA sequencing and then a total of 6513 OTU were defined.According to the species annotation information that compared under various level of classification,the intestinal flora in four different growth stages presented to change,typically between the group of tadpole that living without water and breathe with gill and the group of frog that mainly living in the land.Intestinal flora in tadpoles is mainly composed of Proteobacteria,while Firmicutes occupied the top flora in frog group that have got rid of water.Furthermore,biodiversity also found to be significantly different and tend to a general rule that index rise and reach the peak at the climax of metamorphosis.After then,biodiversity began to decrease and up to the lowest when the host tail absorption and land.Analysis of NDMS and PCoA showed that composition of bacteria between four key stages of development in Microhyla fissipes showed dissimilarity.Accordingly,we speculate that change of environment from aquatic to terrestrial,reconstruction of digestive tract through metamorphosis,and diet from herbivore to meat eating are closely related to the diversity and dissimilarity of the intestinal flora.In this case,we selected group of metamorphosis peak as the representative of aquatic type and the individuals after sexual maturity as the representative of the terrestrial type to further explore the metabolic pathway by metagenomic function analysis.As a result,we found that function of intestinal microbes in different developmental stages was also dissimilar.Microbiota living in herbivorous tadpole would help the host to digest carbohydrates,amino acids,especially riched in carbon metabolism,purine metabolism,pyrimidine metabolism and other substances.Interestingly,bacterium in frog are involved in the similar pathways.However,the degree of participation is lower than tadpole,especially in the use and digestive of protein and we infer that host may own the ability for absorb and use the proteins,lipids and other nutrients than herbivorous tadpole.The composition of the animal intestinal microbial community might vary across developmental stages.In this study,we aimed to research the alterations of microorganisms resident in the digesting tract of Chinese giant salamander(Andrias davidianus)along ages and gastrointestinal tract.135 individuals(age ranging from 1 to 4 years)were used as test animals,and 3,530,075 bacterial 16S rRNA gene gained from 53 samples of contents from four gut region including stomach,duodenum,ileum and rectum.The highest mean abundance of bacterium community in gastrointestinal tract changed along with ages:phyla Bacteroidetes(44.48%)in age 1,Proteobacteria in age 2(32.67%)and age 3(29.95%),and Firmicutes(33.84%)in age 4.An increasing trend was found in the phyla Firmicutes from 13.59%to 33.84%while a decreasing trend was found in Fusobacteria from 23.20%to 1.26%along with the ages.The overall richness of gut bacterial community were increased from age 2 to 4.Moreover,hierarchical cluster analysis revealed that gut microbiome of age 2 were more dissimilar compared to those of age 3 or 4.In addition,communities resident in stomach are more dispersive compared to those in other gastrointestinal tract sections.Gut microbiome dissimilarity across ages in Chinese giant salamander were likely associated with the change of diet(feeding on yolk or red worm before age 2 and shrimp or crab tissues after age 2)and development of digestive tract(from simple to complex).