design: DNA was extracted from samples using MagPure Stool DNA KF Kit B (MAGEN, Guangzhou, China) following manufacturers protocol. Briefly, 100-200 mg sample containing microbial cells were lysed by bead beating followed by chemical lysis at 65 for 20 min. The cell lysate was collected by centrifugation at 14000g for 5 minutes (Eppendorf, Germany) and applied onto magnetic beads in magnetic beads binding solution containing Proteinase K and RNase A. Bound DNA was washed three times before eluted from the beads. The resulting DNA was stored at -20oC freezer until use. Library preparation for metagenomic sequencing was performed using MBIEasey Universal DNA library prep set (MGI-Shenzhen, China) and the resulting DNA library was sequenced using the DNBSEQ-G400/T7/T10 platform (BGI-Shenzhen, China).