Diversity and ecological potentials of viruses inhabiting in the Kermadec and Diamantina trench sediments.

Viruses are the most abundant biological entities in marine ecosystems, playing an important role in biogeochemical cycling and the regulation of microbial dynamics. However, their assembly driving force, genomic evolution, and potential ecological functions in the hadal trench remain largely unknown. Here, 32 359 viral operational taxonomic units were derived from metagenomes of 40 sediment samples in the Kermadec and Diamantina trenches. High novelty and habitat-specific endemism of viruses based on the protein-sharing network analysis were demonstrated. Their auxiliary metabolic genes were involved in the biogeochemical cycles and compensatory metabolic process of the host inferring from the virus-host linkage prediction. Distinct viral community assembly in the two trenches and among different sampling depths was mainly driven by the stochastic processes, especially dispersal limitation. This was further proved by the low genomic mutation rates at deeper depths with potentially high hydrostatic pressures. These niche-dependent distribution patterns and genomic features together reflected the survival and adaptative strategy of viruses. This study provided new insights into the high diversity, ecological potentials, evolution, and adaptive mechanism of viruses in the deep biosphere.