16S rDNA amplicon seq of bacteria: root
Total metagenomic DNA was extracted by using the PowerSoil DNA Isolation Kit, and examined by using 1% agarose gel electrophoresis before the DNA samples were stored at 20C in a freezer. Then an improved dual-index high-throughput sequencing approach with paired-end 250 nt was used to create the sequencing library of 16S rRNA gene (16S rDNA) V3-V4 region.