title: Role of Nutrient Limitation and Viral Interactions on Antarctic Microbial Community Assembly: A Cryoconite Microcosm Study
design: For the nutrient-addition experiment (conducted at University of Colorado -Boulder, USA), we selected cryoconite hole sediments from Canada Glacier, Taylor Valley, Antarctica. TThirty previously collected cryoconite sediment samples in Nov 2016 were bulked and gently homogenized. Homogenized sediments were then distributed among 20 sterile Petri dishes (60 mm), each with 25 g dry weight equivalent (31.25 g wet sediment based on 25% water content). and assigned to five experimental treatments. This sample was a P+, sediments that received 1 ml of sodium phosphate dibasic solution to achieve 2 micro mol P. The treatment incubated in a freeze-thaw growth chamber with temperatures cycling between 1 degrees C and 3 degrees C and light between ~100 Lux (5 hrs/day) and ~10,000 Lux (19 hrs per day) to imitate natural cryoconite holes conditions during austral summers. To keep the sediments from drying out and maintain their wet weight, the plates were watered on weekly basis. The experiment was terminated on the 80th day. Total DNA was extracted from ~300 mg of sediments with a DNeasy PowerSoil Kit (Qiagen Inc., Toronto, Canada) according to manufacturers protocols. The extracted DNA was used to generate Illumina sequencing libraries  the Illumina DNA LP (M) Tag 96 sample preparation kit (Illumina, San Diego, CA, USA) these were sequenced at Psomagen Inc. (Rockville, MD, USA) on an Illumina NovaseqX Psomagen Inc. (USA).