Abstract

Soil viruses represent Earth's most abundant biological entities, yet their contributions to biogeochemical cycling remain poorly understood. This study investigated viral impacts on carbon and nitrogen dynamics through integrated metagenomics, stable isotope probing, and experimental manipulations across agricultural, forest, and grassland soils. We identified 48,726 unique viral operational taxonomic units (vOTUs), with 73% representing novel lineages. Viral-induced bacterial mortality released 2.3-4.8 Pg C annually into soil organic matter pools, contributing 18-31% of microbial necromass formation. N-labeled substrate experiments revealed that viral lysis accelerated nitrogen mineralization rates by 42% through release of cellular contents. Prophage induction under environmental stress doubled carbon flux through the microbial loop. Auxiliary metabolic genes (AMGs) in viral genomes encoded key enzymes for carbon metabolism (glycoside hydrolases) and nitrogen cycling (nitrate reductase, ammonia monooxygenase), directly participating in biogeochemical transformations. Network analysis showed viral predation maintained microbial diversity through "kill-the-winner" dynamics, preventing competitive exclusion and sustaining functional redundancy. Seasonal monitoring demonstrated that viral abundance peaked during rapid plant growth phases, coinciding with enhanced nutrient cycling. These findings reveal viruses as critical yet overlooked drivers of soil carbon sequestration and nitrogen availability, with implications for ecosystem modeling and sustainable agriculture.