In spite of low temperatures, limited amount of nutrients and availability of water, a great biological diversity is hidden in the glaciers. Glacial microbial communities are dominated by bacteria, algae and fungi, and also viruses. Knowledge of viruses in these extreme environments is limited, and new research is needed to better understand their role and diversity. In this master's thesis, we performed a virome analysis of samples from the Triglav and Skuta glacier. Ribonucleic acids (RNA) were isolated from concentrated samples of Slovenian glaciers, amplified with random oligonucleotide primers and sequenced using the Illumina platform. We also acquired data from publicly available databases obtained by sequencing samples of Icelandic glaciers. Using bioinformatics analyses, we searched for viral sequences in obtained data and classified them taxonomically. The percentages of reads classified as viral were low in samples from Slovenian and Icelandic glaciers. Even though the entire process of virome analysis was aimed at RNA viruses, in all samples of Slovenian glaciers, we most abundantly detected reads of bacteriophages, classified within Duplodnaviria realm. The identities of viral sequences detected in samples from Slovenian and Icelandic glaciers showed low similarities with known viral sequences from existing databases, indicating the presence of many new viral species. Some viral contigs (from toti-like and amalga-like viral groups) potentially represent the entire genomes of newly discovered viruses. In some samples from Slovenian glaciers, reverse transcription quantitative polymerase chain reaction analysis confirmed the presence of pepper mild mottle virus nucleic acids, which is used also as a viral fecal indicator. Taken together, analysis of the viromes of Slovenian and Icelandic glaciers showed a great diversity of virus sequences and the presence of many new viruses.
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