title: Amplicon sequencing: prokaryotic V4 region of 16S rRNA gene
design: PCR used primers 515F - 806R (Apprill et al. 2015, Parada et al. 2016) customized for Illumina dual indexing of amplicons in a single PCR step (Kozich et al. 2013)  with Promega GoTaq PCR Core Systems reagents