Metagenomics of human saliva
Total DNA was extracted from saliva sample using the QIAamp Fast DNA Mini Kit (Qiagen, Hilden, Germany) following the manufacturers instructions. DNA concentration and integrity were assessed by a NanoDrop2000 spectrophotometer (Thermo Fisher Scientific, Waltham, MA, USA) and agarose gel electrophoresis, respectively. DNA was fragmented by S292 Focused-ultrasonicators (Covaris, USA) and cleaned up by Agencourt AMPure XP beads (Beckman Coulter Co., USA). Then the libraries were constructed using TruSeq Nano DNA LT Sample Prepararion Kit (Illumina, San Diego, CA, USA) according to the manufacturers instructions. The Metagenome sequencing and analysis were conducted by OE Biotech Co., Ltd. (Shanghai, China).