Comparative Study On The Gastric Microbiota Diversity In Small Mammals

The composition of the gastrointestinal microbiota is known as the second set of genomes in animal evolution.It plays an important role in energy metabolism,immune regulation,and defense against pathogen invasion.General common sense believes that the stomach of vertebrates is the most powerful barrier for the ingestion of microbiota from the oral cavity.Some people even believe that in this strong acid environment,few microbiota can survive,so it is an approximately sterile environment.However,recent studies have revealed a high degree of diversity in the stomach microbiota of healthy humans.The Firmicutes,Actinomycetes,Bacteroides,and Proteobacteria are the major constituent members of the human gastric flora.The most representative genera are Lactobacillus,Streptococcus and Propionibacterium.However,little research has been done on the composition of the stomach flora of other mammals.During the evolution of mammals,there have been many ecological and dietary transfers from terrestrial to aquatic environments.During these important biological and ecological learning transfers,the stomach is as the first step of food entering the digestive system,and the adaptive changes of the microbiome inside it need to be revealed.In recent years,the development of high-throughput sequencing technology has gradually replaced the traditional medium-based technology as the main means to study the above scientific issues.In this study,we used high-throughput sequencing technology as the method to research mammalian Insectivora which is a representative species with different ecological learning in the most primitive taxonomic unit of this living group,and compared it with the most primitive rodent.The purpose of this study is to reveal the adaptive changes in the composition of the stomach microbiota in the process of important ecological transfer of small mammals(terrestrial to semi-aquatic,meat-to-vegetative).Representative species studied include the insectivorous Crocidura attenuata(Milne-Edwards,1872),Anourosorex squamipes(Milne-Edwards,1872),Uropsilus gracilis(Thomas,1911),Chimarrogale leander(Gray,1842)and Rodentia Typhlomys cinereus(Milne-Edwards,1877)in Platacanthomyidae.These species show significant ecological differentiation.In addition,the evolution of the Insectivora has occurred from the terrestrial environment to the aquatic environment.Little is known about the adaptive changes of the stomach microbial flora in the process of these important ecological learning transfer.Regarding all these aspects,we try to use systematic biology,microbiology and bio-informatics to get deeper understanding.The composition,diversity and function of the stomach microbes in C.attenuata,A.squamipes,U.gracilis,Ch.leander and T.cinereus are discussed,and the effects of different ecological types on stomach microbes in small mammals are also discussed.In response to the above scientific issues,this research is based on the 16 S rDNA amplicon sequencing technique.A total of 843 MB data was obtained by sequencing,and the effective data reaches more than 95.7%.By using RDP classifier,all the sequences could be classified into 23 phylum,36 classes,69 orders,158 families,396 genera and 606 species.The most important eight phyla are Proteobacteria(34.1%),Firmicutes(29.7%),Cyanobacteria(0.4%),Bacteroidetes(17.5%),Actinobacteria(6.4%),Fusobacteria(0.7%)and Chlamydiae.Acidobacteria(2.4%).The results show that the microbiota composition of these species differ in the alpha diversity,in addition,there are significant differences in beta diversity.There are differences in the genetic structure composition among the groups.The T.cinereus is far away from the other four groups,and there are also differences in the ecological niche structure composition among the groups.The Ch.leander is far away from the other three species of the same order.At the phylum level,the relative abundance of the samples in each group is significantly different,including Proteobacteria,Bacteroidetes,Cyanobacteria and Firmicutes.Furthermore,we used phylogenetic investigation of communities by reconstruction of unobserved states to predict functional profiles of those microbes.The results present that they perform similar functions,which are main involved in genetic information processing,environmental information processing,metabolism,organismal systems,human disease,cellular processes.However,these attempts are based on 16 S rDNA sequences.The actual interaction and function of microbiota still need to be directly analyzed by functional genomics and other technologies.In this paper,the study on the basic composition and influencing factors of microbes in small mammals provides an important reference for revealing the role of gasic microbes in the adaptation process of genetic and niche transfer.