The Influence Of Altitude On The Symbiotic Microorganisms (body Surface And Intestinal Microorganisms) Of Amphibian

Symbiotic microbes play an important role in the animal's nutrition intake,growth and development,individual health,and disease immune.In recent years,the potential coevolution between animal symbiotic microorganisms(such as intestine,skin microbes)and environmental factors(such as altitude,temperature)is one of the basic scientific questions in microbial ecology.It is pointed out that there are obvious differences in the composition and structure of the flora and the structure of the symbiotic microorganisms(skin and intestinal microbes)at different elevations.The altitude can also reduce host microbial community diversity.Current studies focus on mammals and birds,but less on amphibians.Given the interesting of this scientific question(co-evolution between the host and its symbiotic microorganisms),we have studied the symbiotic microorganisms(skin and intestinal tract)of wild amphibians at different altitudes by high-throughput sequencing(MISEQ technique of bacterial 16 s ribosomal gene)in order to provide some basic data.(1)In the low-altitude areas,we selected seven sampling sites in Leshan in May 2018(altitude range of 360,446 meters),and collected five amphibious species(e.g.,Bufo gargarizans,Microhyla ornata,Pelophylax nigromaculata,Rana omeimontis,Fejervarya limnocharis).A total of 155 samples(including,skin,gut,water and soil microbes)were obtained.The results showed that different species at low altitude were mainly composed of: Bacteroides and Firmicutes followed by Proteobacteria.There were significant differences in the abundance of some microbial groups(e.g.,Bacteroidetes,Bacteroides,Citrobacter)and ?-diversity(Chao1 index)between different species.This phenomenon may be due to the existence of some genetic distance among the five amphibious species selected in this experiment.However,the gut microbial similarity on overall microbial community were high among these species which may be due to high-similarity of habitats among these locations..(2)In high altitude areas,we selected three sampling sites at Kangdingliqiu River basin in July 2018(altitude range of 3340.3989 meters).We collected five amphibian species(e.g.,Bufo gargarizans,Scutiger boulengeri,Batrachuperus tibetanus,Amolops xinduqiao,Nanorana pleskei).A total of 46 samples(including,skin,gut,water and soil microbes)were obtained.The results showed that the common predominant microbiome among different species at high altitude was composed of: Bacteroides and Firmicutes followed by Proteobacteria.In addition,we found that there was little difference in composition and ? diversity of symbiotic microorganisms(skin and gut)at high altitude,especially in skin microbes.We speculate that this may be due to the direct exposure of surface microorganisms of amphibious species at high altitude to the environment,which is susceptible to environmental stress,resulting in similar characteristics.g sites.(3)Several interesting phenomena have been found after comparing the symbiotic microorganisms between low and high elevations.a.The particular symbiotic microbial groups might reflect the selection by high altitude environment: we have found several bacteria living in extreme environments in the skin microbes at high altitudes,such as the Halomonadaceae,Caulobacteraceae,Sphingomonadaceae.So the presence of these bacteria might reflect the selectivity of high altitude extreme environments to the composition of the skin microbes of amphibians;b.The high altitude selection might contribute to the decrease in the alpha and beta diversity in the symbiotic microbiome.For instance,the observed OTU numbers in the skin and intestine at high altitude was significantly lower than that at low altitude.Therefore,we speculate that the high altitude area might represent a vast and complex natural selection force that affected the symbiotic microorganisms of animals;c.The particular phenotypes of symbiotic bacteria might reflect the adaptation on the high altitude environment.For example,we found that high altitude symbiotic microbes had low oxidase stress tolerance and potentially pathogenic as well as higher energy metabolism.Moreover,the high proportion of biofilm forming,can help amphibians adapt to the extreme environment of low temperature and hypoxia,but this phenomenon was not found in the intestinal tract at high altitude;d.Skin and gut microbiomes have differentiated ecological niches: amphibian skin and intestinal microbes live in different parts,showing different niche and microbial community.However,because they live in the same environment,they have some common characteristics,such as low oxidase stress tolerance and potentially pathogenic.Conclusion: the altitude had a significant effect on the symbiotic microbes of amphibians,especially in the skin microbiome.High altitude would be a selective force and lead to decreasing in the alpha and beta diversity in these symbiotic microbiomes.Some enriched microbiomes(e.g.,Halomonadaceae,Caulobacteraceae,Sphingomona-daceae)in high altitude amphibians might reflect the selection by high altitude environment.Although the distinct microbial structure between the skin and gut microbiomes,both of them in high altitude environment possibly co-evolved to some convergent characters or functions(such as low oxidase stress tolerance,low potentially pathogenic,and high energy metabolism).These characters might be associated with the host's health and help host adapt to the high altitude living.The interaction between animal and their symbiotic microbiomes is complicated in the different habitat.In the future,the understanding of this interaction in the wild species will be integrated more putative ecological factors(e.g.,habitat selection,life history,and feed behavior).