title: initial microbial community in refinery sludge before start of experiment
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