Deep-soil viruses regulate carbon cycling in global soil profiles

Viruses in deep soil can act as regulators of the microbial carbon pump by helping microbial hosts scavenge carbon and promoting the formation of mineral-associated organic carbon, according to a soil-profile survey and a global synthesis of metagenomic data. The study found that viral richness increased significantly with depth even as carbon availability declined, while a global analysis of 138 soil profiles identified a positive association between viral abundance and soil organic carbon.

The research combined a survey of 216 metagenomes from profiles extending from 0 to 700 cm in four agroecosystems with a global synthesis of subsurface metagenomes. This work produced the Deep Soil Viral Resources Database, which contains 50,949 viral operational taxonomic units and 3,902 auxiliary metabolic genes, abbreviated as AMGs. Together, the two analytical components were used to examine how viral diversity, activity and encoded metabolic functions vary through soil profiles and how those patterns relate to carbon cycling at global scale.

Depth was associated with both increasing viral richness and a shift toward lysogeny. The deep-soil virome also carried AMGs and lysozymes involved in polymer degradation and cell endolysis. The AMGs were linked to facilitation of carbon scavenging by bacterial hosts, providing a potential mechanism through which viruses could affect microbial carbon acquisition when carbon availability is lower. This functional role was distinct from the observed global association: the survey data identified viral genetic functions and their relationship to host carbon use, whereas the global synthesis tested the broader relationship between viral abundance and soil organic carbon.

Viral endolysin provided a second mechanism in the proposed framework. The reported experiments found that viral endolysin significantly promoted necromass carbon accumulation, and that this contribution was associated with increases in mineral-associated organic carbon. These results connect virus-induced cellular breakdown with the transfer of microbial carbon into a pool associated with minerals. The authors therefore propose that viruses strengthen the microbial carbon pump in deep soils through two complementary processes: AMGs facilitate host carbon scavenging, while endolysin activity promotes necromass formation.

The global analysis provided evidence consistent with this framework. Across 138 soil profiles, viral abundance had a positive effect on soil organic carbon, while the depth-related patterns in microbial carbon utilization were examined as potential drivers of the virome. However, the broad synthesis demonstrates an association across soils rather than showing that viral abundance alone causes carbon retention. Likewise, the profile survey was conducted in four agroecosystems, so its mechanistic results may not represent every deep-soil environment. Within those limits, the study establishes viruses as important regulators of subsurface carbon cycling and offers a framework for assessing their contribution to deep-soil carbon persistence.

Subject of Research: Viral regulation of microbial carbon cycling in deep-soil profiles

Article Title: Soil viruses as key regulators of the microbial carbon pump in deep soils

Article References: Wu, X.-J., Han, W.-X., Liang, C., Chen, J., Nicol, G., Rillig, M. C., Zhu, D., Liu, B.-B., Wang, F.-H., Xiao, K.-Q., & Zhu, Y.-G. (2026). Soil viruses as key regulators of the microbial carbon pump in deep soils. Nature Ecology & Evolution. https://doi.org/10.1038/s41559-026-03207-x

Image Credits: AI Generated

DOI: 10.1038/s41559-026-03207-x

Keywords: soil viruses, deep soils, microbial carbon pump, soil carbon cycling, auxiliary metabolic genes, viral endolysin, necromass carbon, mineral-associated organic carbon, metagenomics, Soil, viruses, regulators