Crude oil polluted soil
DNA was extracted from the soil sample (0.25 g) using DNeasy Power Soil DNA Isolation Kit (Qiagen, Hilden, Germany) following the manufacturers instructions. The extracted DNA samples were sequenced at MR DNA (www.mrdnalab.com,  Shallowater, TX) on MiSeq following the manufacturers guidelines. In summary, the V1-V3 variable region of 16S rRNA gene were amplified using the primers 8F-519R with barcode on the forward primer in a 30 cycle PCR. PCR amplifications were performed using the HotStarTaq Plus Master Mix Kit (Qiagen, Germantown, MD) under the following conditions: 94 C for 3 min, followed by 30 cycles of 94 C for 30 s, 53 C for 40 s and 72 C for 1 min, followed by a final elongation step at 72 C for 5 min. After amplification, PCR products were checked in 2 % agarose gel to determine the success of amplification and the relative intensity of bands. Multiple samples were pooled together in equal proportions using MR DNAs proprietary molarity model and purified using calibrated Ampure XP beads, before preparing the illumina DNA library. Sequence data were processed using version 2019_05 of MR DNA taxonomic analysis pipeline and database.