To extract DNA from environmental microorganisms, we used GenEluteTM Bacterial Genomic DNA KIT (Sigma- Aldrich, Missouri, USA). For field samples, we used the modified gram-positive extraction procedure described by the manufacture. After filtration and sonication, we centrifuged samples for 2 min at 12,000 RPM without the overnight enrichment step recommended by the manufacturer, to preserve original concentrations. Pelleted cells were resuspended in 200 mL of lysozyme solution and incubated for 30 min at 37 °C. We then added 20 µL of Proteinase K solution to the sample, followed by 200 µL of lysis solution, then incubated at 55 °C for 10 min after thorough vortexing. Columns were prepared by adding 500 µL of the column preparation solution to each pre-assembled GenElute Miniprep Binding Column and centrifuging for 1 min at 12,000 RPM. We then added 200 µL of 95 % ethanol to the lysate and mixed thoroughly. The entire lysate was transferred into the binding column and centrifuged at 12,000 RPM for 1 min, after which the column was placed in a new collection tube and 500 µL of wash solution # 1 was added to the column and centrifuged for 1 min at 12,000 RPM. After discarding the eluate, we placed 500 µL of wash solution # 2 into the binding column and centrifuged for 3 min at 12,000 RPM. For DNA elution, we poured 200 µL of elution solution onto the column and allowed it to incubate for 5 min at room temperature, then centrifuged it for 1 min at 8,000 g. DNA concentration was estimated using a NanodropTM 1000 (Thermo-Scientific, Ramsey, Minnesota).