library_construction_protocol: The 16S rRNA gene was amplified using the following primers with the sample-specific 8-base tag sequence: 8F (AGA GTT TGA TYM TGG CTC AG) and 338R (TGC TGC CTC CCG TAG GAG T). PCR amplification was carried out using KOD DNA polymerase. Reads were excluded from the analysis if they were shorter than 100 bases or did not include the correct forward and reverse primer sequences.