title: 16S amplicon of microbial community : negative control
design: negative extraction control of  FastDNA Spin Kit for Soil, first amplification of a region of the rRNA 16S gene with 515F/926R primer pair  (5-GTGCCAGCMGCCGCGGTAA-3/5-CCGYCAATTYMTTTRAGTTT-3), second amplification to add Illumina adaptors, sequencing 2*300 PE, Illumina MiSeq Reagent Kit v3