title: Metagenomic sequencing of Missouri maize soils: bacteria Bradford upper depth time 3 rep 1 no nitrogen
design: Soil microbial DNA was extracted using the MoBio PowerSoil DNA Isolation Kit with slight modifications as recommended by Lindahl et al. (2013). Samples were homogenized using a Vortex-Genie 2 Mixer for 10 to 15 minutes. The DNA templates were quantified using an ND1000 spectrophotometer and then concentrated to a final concentration of 30 ng l-1. For amplicon library generation, the V4 hypervariable region of the 16S rRNA gene was targeted for bacterial molecular identification. The primers 16Sf and 16Sr, which contained 8-bp barcodes, were used for dual-indexed Illumina sequencing. AccuPrime Pfx SuperMix was employed for 16S amplicon generation, and gel electrophoresis was performed for confirmation. The samples were sequenced at the Brigham Young University DNA sequencing center using paired-end sequencing (2x250) on the Illumina HiSeq 2500 platform (Illumina Biotechnology, San Diego, CA, USA).