DNA extraction blank  (16S rRNA gene amplicon sequences)
PCR reactions consisted of 2.5 uL of 10 x standard Taq buffer, 0.5 uL of 10 mM dNTP, 0.25 uL of BSA (20 mg/mL), 5 uL of 1 uM of forward primer (515FB: GTGYCAGCMGCCGCGGTAA), 5 uL of 1 uM of reverse primer (806RB: GGACTACNVGGGTWTCTAAT), 5 uL of DNA, 0.2 uL of Taw DNA polymerase, and 6.55 uL of PCR water. PCR reaction conditions were: 95 C for 5 min; 35 cycles of 95C for 30 s, 50C for 30 s, 72C for 50 s; 72C for 10 min. Triplicate PCR products were polled and resolved with 2% TAE agarose gel. PCR products in amount of correct amplicons were pooled, gel purified, and quantified using Qubit dsDNA HS Assay Kit. Library DNA was sequenced with MiSeq Reagent Kit v2 (2 x 250 cycles).