design: Water samples were collected from continuous reactors prior and post one month treatments which consisted of feeding the reactors either with artificial lake water media and continuous acetate or with pulses of acetate, each treatment had in total 6 replicates. A total of 10 mL of water was collected from each reactor by vacuum filtration through 0.2 µm Supor 200 filters (Pall Corporation, Port Washington, NY, USA). Filters were stored at – 80 ̊C until DNA extraction was performed using the Power Soil DNA isolation kit as recommended by the manufacturer (MoBio Laboratories, Carlsbad, CA, USA). Each sample was initially amplified in duplicates using bacterial primer constructs targeting the variable V4 region of the 16S rRNA gene. Duplicates were pooled and purified using the Agencourt AMPure (Beckman Coulter) as recommended by the manufacturer, and then used as template in a second PCR step in order to attach standard Illumina handles and index/barcode primers N4-341F and N4-805R. PCR products were purified in the same fashion.