design: The extracted DNA was used to construct the 16S rRNA gene library by amplifying the V4 16S rRNA gene following the protocol from the Schloss lab. The amplified DNA was then normalized using the SequalPrep Normalization Plate (Invitrogen) and pooled to form a single librart. The Ilumina MiSeq (2x250, paired-end) was used to sequence the 16S rRNA gene amplicons.