16s rRNA of human: adult male oral
A total of 2-5 mL of the patients saliva was collected by the same dentist and was immediately frozen in liquid nitrogen and stored at -80. Genomic DNA was extracted by using a Qiagen DNA isolation kit. Extracted DNA was used as a template to amplify the V3-4 region of 16s rDNA genes for sequencing by using the Illumina HiSeq 2501 platform at CapitalBio (Beijing, China).