The corrosion deposits on the surfaces of the pipeline cookies (the surfaces corresponding to the interior of the pipeline which was in contact with the fluid flow) were removed by scraping with a sterile metal spatula into a sterile Petri dish in a UV-irradiated chamber. The resulting debris was transferred to sterile 1.5ml plastic centrifuge tubes, and the dry weight of each sample was recorded. The surfaces of cookies from which deposits were removed were covered with 250μl of DNAzol (Direct Molecular Research Center, Inc., Cincinnati, OH, USA) for 5min. Following incubation, the DNAzol was removed from the cookie surface by pipette, transferred into a sterile 1.5ml tube, and used for DNA extraction.