Impact of Virus-Mediated Modifications in Bacterial Communities on the Accumulation of Soil Organic Carbon.

Microbial adaptations to resource availability are crucial to predict the responses of ecosystems to carbon (C) changes, yet viral roles in C cycling under varying levels of C remain elusive. Through metagenomic analysis of soils with contrasting C availability, a total of 24,789 viral contigs predominantly represent Microviridae and Siphoviridae. The soils with low C availability (straw removal) harbored 21% lysogenic viruses and enriched auxiliary metabolic genes (AMGs) related to C degradation (p < 0.05). Conversely, the soils with high C availability (straw returning) show 93% lytic viruses, stronger virus-bacteria symbiosis, and numerous host functional genes related to C cycling and viral AMGs linked to C fixation (p < 0.05). Furthermore, these findings show that the addition of viruses boosted microbial metabolic efficiency and recalcitrant C accumulation (p < 0.05), with lytic activity accelerating organic C turnover via nutrient release and necromass formation. Overall, this study demonstrates viruses as key regulators of sustainable sequestration of C through host-driven metabolic optimization.