Metagenomic Analysis Of Microbiota In Deep-dentine Caries Of Young Permanent Molar

Objectives:Deep caries is a common type of caries,because of its deep caries degree,cariogenic bacteria can invade the deep dentin,easy to cause caries pulpitis.In this study,the species composition and functional characteristics of microorganisms in deep caries of young permanent molars were analyzed by using the method of macrogenomics high throughput sequencing,and the differences of microorganisms in samples from different depths of deep caries of young permanent molars were compared.Materials and Methods:The shallow and deep samples of deep caries of young permanent molars we are collected,the DNA was extracted and the database was built.The high through put sequencing technique of Illumina platform was used to sequence,and the MetaGenMark software was used to predict the gene.DIAMOND software was used to annotate species and function in MicroNR database and KEGG database respectively.a variety of statistical methods were used to analyze and compare the species composition and functional characteristics of oral flora in deep caries of young permanent molars.Results:1.In this study,some microbial gene sets of deep caries in young permanent molars were established by macrogenome high-throughput sequencing.A total of 64.1 Gb sequencing data were obtained.The average sequencing data of each young permanent molar deep caries sample was 6.41 GB.After sequence assembly and gene prediction,514496 non-redundant genes were obtained.2.A total of 85 phylum,62 classes,137 orders,274 families,981 genus and 3869 species of bacteria were detected in the samples of deep caries of young permanent molars by metagenome high-throughput sequencing.3.In the deep caries samples of young permanent molars,the dominant phylum with high abundance were Frmicutes,(39%),Actinobacteria,(33.9%),Ba cteroidetes,(9.2%)and Proteobacteria,(4.1%),Fusobacteria,(3.7%).These five dominant bacteria could be detected in 10 dentin caries samples with high abundance,and the content of these five dominant bacteria accounted for more than 90% of the whole dentin caries.It can be considered as the main structural flora of young permanent molars with deep caries.4.The dominant genus of top10 in the deep and shallow samples of young permanent molars with deep caries were Lactobacillus(23.1%),Propionibacterium(11.5%),Olsenella(10.4%)and Actinomyces(7.0%),Streptococcus(6.4%),Prevotella(4.7%),Selenomonas(2.0%),Parascardovia(1.8%),Lepto trichia(1.6%),Veillonella(1.7%).5.The dominant strains of species abundance top10 in young permanent molar deep caries samples were propionic acid bacteria(11.3%,Streptococcus mutans(4.7%),Lactobacillus gallisepticus(5.2%),Olsenella profuse(4.3%),Lactoba cillus vaginalis(2.1%),Lactobacillus oris(2.0%),Parascardovia denticolens(1.8%),Olsenella umbonate(1.6%),Lactobacillus ultunensis(1.5%)and Lactobacillus salivarius(1.1%).6.There was no significant difference in microbial species diversity between deep and shallow layers of young permanent molars with deep caries at the phylum,genus and species levels(P>0.05).7.In this study,there was no significant difference between shallow and deep microorganisms in deep caries of young permanent molars at the level of fun ctional genes.The results of gene collection and KEGG database annotation comparison showed that there was no significant difference between shallow and deep microorganisms in deep caries of young permanent molars.The proportion of functional genes related to carbohydrate metabolism and amino acid metabolism was the highest in young permanent molars,accounting for 5.75% and 5.41%,respectively.Conclusions:1.The high throughput sequencing technique of macrogenomics can effectively analyze the rich species diversity and functional characteristics of oral microecology in young permanent molars with deep caries.2.There was no significant difference in species composition and functional gene between shallow and deep microorganisms in deep caries of young permanent molars.3.The functional genes of oral microorganisms in deep caries of young permanent molars are mainly distributed in carbohydrate metabolism and amino acid metabolism pathway.