Samples (1 liter) were vacuum concentrated (5 kPa) onto 47 mm 0.45 µm Durapore polyvinylidene fluoride membrane filters (Millipore). The filters were frozen immediately in liquid nitrogen and transported frozen to McMurdo Station, where they were stored at -80 degrees C until DNA extraction.
Lake Bonney in the McMurdo Dry Valleys (Antarctica). Samples were collected at 6, 13, 18, and 20m in the east lobe (ELB) and 10, 13, 15, and 20m in the west lobe (WLB) of Lake Bonney from February to April 2008. All collection depths are relative to the piezometric water level in the ice borehole.
DNA was isolated from a whole filter using the MP DNA kit (MP Biomedicals, CA) following the kit’s instruction. Sequencing was performed using the BigDye Terminator v3.1 cycle sequencing kit (ABI, CA) with M13R primer and the fragments were sequenced on an Applied Biosystems 3730×l DNA Analyzer (ABI, CA). The 18S rRNA gene sequences reported in the current study have been deposited in GenBank under accession numbers GU969060 to GU969102.