title: Enrichment with 50 mM nitrate anaerobically
design: V4 region of 16 S rRNA gene (primers 515F and  806R) amplified from metagenome extracted from each sample using AmpliTaq 360  MM mastermix and annealing temperature of 50 degree C. Forward primers were  bar-coded. Amplified products purified through E-gel , all samples pooled in  equimolar concentration and processes through OT2 enrichment and subsequent  sampling according to manufacturer's guidelines