16S rRNA pyrosequencing of microbial community
Variable regions 3 to 4 (V3–V4) of bacterial 16S rRNA gene were amplified with the specific primers 341F and 806R.The PCR products of each sample were pooled in equimolar concentrations and purified using a Qiagen Gel Extraction Kit (Qiagen, Germany). Sequencing libraries were generated with TruSeq® DNA PCR-Free Sample Preparation Kit (Illumina, USA) following the manufacturer's instructions, and then sequenced on an Illumina HiSeq2500 platform.