Abstract: Objective: To study the oral microbial community structure in caries-active and caries-free objects using 16S rRNA high-throughput sequencing. Methods: 14 volunteers in Kangle County, Gansu Province were selected, 7 caries- active cases (DMFT≥4, CA group), 7 caries-free cases (CF group), saliva DNA were extracted and PCR amplification. Using Illumina Miseq sequencing platform, two-terminal sequencing of V4 areas of 16S rRNA was carried; diversity of community structure was analyzed using the software such as Mothur, MEGAN4, Cluster 3.0 and Java Treeview software. Results: In total, 118151 measured sequences, 5738 OTUs and 2795 species were found in 10 samples, belonging to 27 phyla, 218 genera. There were some discrepancies between CA group and CF group, at the phylum level, Firmicutes and SR1 in CA group were lower than in CF group. At the genus level, Rothia, Alistipes and Catonella in CA group were lower than in CF group. Scardovia in CA group was higher than in CF group;OTUs were 550.2±26.48 in CA group and 597.4±66.07 in CF group, Simpson index was 0.73±0.03 in CA group and 0.49±0.01 in CF group, but both of them had no statistical difference between the two groups. Conclusion: The microbial community structure in saliva were complicated; the variety in CA group was lower than that in CF group; The existence of Rothia, Alistipes and Catonella et al. had a negative correlation with caries, otherwise Scardovia et al. had a positive correlation with caries.

Key words: Caries , Microbial community structure 16S , rRNA, High-throughput sequencing Saliva