title: 16s DNA of drinking water and distribution system biofilm
design: sample was filtered with a 0.22 mm polycarbonate membrane (25 mm in diameter) to collect biomass for DNA extraction. The total DNA was extracted from the membranes with a FastDNA SPIN Kit for Soil (Mpbio, Santa Ana, California, USA) according to the manufacturer's protocol. The concentration and purity of the total DNA were measured by a NanoDrop NC2000 spectrophotometry (Thermo Fisher Scientific, Wilmington, Delaware, USA)