title: PlastispherePP-S, replicate 2
design: We added 100 g of soil from each microcosm under six treatments to a 500-mL beaker placed in a Petri dish (diameter: 180 mm, height: 90 mm), and about 400 mL of sterilized saline water solution was added. After stirred manually for 5 minutes following a settling time of 1 hour, the floated MPs were overflowed to Petri dish by continued saline water increment. The flotation liquids were collected and filtered through a nylon filter with a pore size of 20 m after repeated separation twice. MP-contained mixtures were washed into the clean and aseptic tubes from filters using 30 mL sterilized saline water prior to centrifugation at 8000g for 10 min. In order to purify the MPs particles, the floated MPs were transferred to a new tube and washed with sterilized saline water again. After sieved through a 0.9-mm stainless steel mesh, the purified MPs were transferred to a 15 mL clean and aseptic tubes for centrifugation again at 8000g for 10 min. Afterward, the floated MPs were collected and filtered through a nylon filter prior to a final sterilized saline water rinse. DNA was extracted from MPs particles and soil samples using the FastDNA Spin Kit for Soil (MP Biomedicals, CA, USA) according to the manufacturers protocol. In total, 0.5 g soil samples and 0.2 g MPs particles were used for DNA extraction in triplicate.