Unique ecological functions of viral communities potentially influence microbial adaptability in deep-sea ferromanganese nodule deposits.

Ferromanganese nodule deposits represent unique deep-sea habitats characterized by metal-rich environments. However, the composition and ecological functions of viral communities inhabiting the regions remain poorly understood. Here, we investigated the composition, distribution patterns, and potential ecological roles of viral community in both sediments and nodules from ferromanganese nodule deposits. Our results indicated that viral community distribution was influenced by sediment depth, habitat type, and microbial community. Furthermore, viruses may enhance the environmental adaptability of microbial hosts by encoding auxiliary metabolic genes, thereby indirectly influencing the biogeochemical cycles of carbon, phosphorus, and sulfur. Notably, viral genomes in ferromanganese nodule deposits contained a high frequency of metal resistance genes (MRGs). At the viral operational taxonomic unit (vOTU) level, the proportion of MRG- encoding vOTUs was 2.46-67.50 times higher in deep-sea habitats than in other marine environments, suggesting potential horizontal gene transfer of MRGs between hosts in sediments and ferromanganese nodules. Laboratory experiments confirmed that some virus-encoded MRGs could significantly enhance microbial metal resistance. Overall, this study provides a comprehensive characterization of viral communities in ferromanganese nodule deposits, highlighting their role in microbial adaptation and providing valuable insights for environmental impact assessments of deep-sea mining.