The Hidden Viral Network: How Viruses Shape Microbial Adaptability and Biogeochemical Cycling in the Polyextreme...

Viruses play essential roles in shaping the structure and function of microbial communities, including those inhabiting extreme environments. The Qaidam Basin is a unique Mars-analog desert characterised by hyperaridity, oligotrophy and high soil salinity. We hypothesise that viruses contribute to microbial adaptability and biogeochemical cycling through virus-host interactions in desert ecosystems. Here, we investigated viral diversity, biogeography, life strategies and interactions with soil microbiomes across the Qaidam Basin. Soil properties, such as water content, pH and mineral assemblages, significantly influenced the distribution patterns of both viral and prokaryotic communities. Broad host range may confer fitness advantages for viruses in deserts where host biomass is limited. Most viruses were characterised as lytic and infected dominant microbial phyla, supporting the "Kill-The-Winner" model, which suggests viral regulation in microbial community diversity and stability. We identified over 32,000 potential viral auxiliary metabolic genes (AMGs), including key genes involved in carbohydrate metabolism, carbon fixation, photosynthesis and phosphorus cycling. Moreover, AMGs related to the biosynthesis of antibiotics, pigments and alkaloids may enhance the adaptability of hosts under extreme conditions. This study unveils the enigmatic virosphere of the Mars-analog Qaidam Basin and underscores the roles of viruses in promoting microbial adaptability and driving biogeochemical cycling.