Fig. 4

Taxonomies (a), communities (b), and host linkages (c–f) of 33 vOTUs recovered from two glacier ice samples. a Viral taxonomy was assigned by comparing genome-content-based network analysis of the 33 glacier vOTUs and 2304 known viral genomes in the NCBI RefSeq database using vConTACT v2 (see “Materials and methods”). vOTUs were classified into three groups: “Singletons” (gray) that had no close relatives; “Exclusive VCs” (black) that were viral clusters (VCs) of exclusively glacier ice vOTUs; and “Classified VCs” (blue) which included glacier ice vOTUs and Refseq viral genomes. b The normalized coverage of these 33 vOTUs was generated by mapping quality-controlled reads to vOTUs, and was normalized to per gigabase of metagenome. c–f Relative abundances of three abundant (>1.0%) microbial genera and their viruses: c Methylobacterium in D25, d Methylobacterium in D49, e Janthinobacterium in D25, and f Sphingomonas in D49. Relative abundances of microbes are based on 16S rRNA amplicon sequencing, and vOTUs are based on their coverages generated by mapping quality-controlled reads to vOTUs. Viruses were linked to hosts in silico by three methods: Blastn, VirHostMatcher, and CRISPR matches (see “Materials and methods”)