Diversity, Function and Activity of DNA Viruses in the Qiangyong Proglacial Lake Sediment, the Tibetan Plateau.

Viruses are the most abundant biological entities on Earth and play crucial roles in regulating ecosystem processes and biogeochemical cycling. Proglacial lakes-key components of cryosphere aquatic systems-host diverse microbial communities despite extreme environmental conditions. However, the composition and ecological roles of DNA viral communities in proglacial lake sediments remain poorly understood. In this study, we applied metagenomic and metatranscriptomic approaches to investigate the diversity, function, activity and host interactions of DNA viruses in sediments from Qiangyong proglacial lake on the Tibetan Plateau. We recovered 4039 viral operational taxonomic units (vOTUs), with 76.6% unclassified at the family level, highlighting a vast reservoir of uncharacterized viral lineages. Host prediction linked 1.8% of vOTUs to key microbial taxa involved in carbon, nitrogen and sulphur cycling. We identified a broad array of virus-encoded auxiliary metabolic genes (AMGs) involved in host resource utilization and metabolic transformation. Moreover, 63 AMGs not previously reported in the literature were discovered, significantly expanding the known viral functional gene repertoire. These findings offer new insights into the diversity and ecological potential of sediment-associated DNA viruses in proglacial lakes, and emphasize their possible roles in shaping microbial communities and influencing biogeochemical processes in cold-region ecosystems.