Under ice sea water MC
For MiSeq sequencing, the V3-V4 hypervariable region of 16S ribosomal RNA gene was amplified with a polymerase chain reaction, using the universal primers for prokaryotes U519F2 (5-CAGCMGCCGCGGTAAHWC-3) U806R2 (5-GGACTACHVGGGTWTCTAAT-3). The 16S rRNA gene libraries were sequenced with single 300 bp end reads on the MiSeq systems (Illumina Inc, San Diego, CA, USA), using MiSeq v3 reagent kits. A two-step polymerase chain reaction and Illumina MiSeq paired-end multiplex sequencing were performed at the sequencing service FISABIO, Valencia, Spain (http://fisabio.san.gva.es/en/servicios).