Expanding the potential soil carbon sink: unraveling carbon sequestration accessory genes in vermicompost phages

The compost microbiome is important in regulating soil carbon sequestration. However, there is limited information concerning phage communities and phage-encoded auxiliary metabolic genes (AMGs) in compost-applied soils. We combined metagenomics and meta-viromes to explore the potential role of bacterial and phage communities in carbon sequestration in the compost microbiome. The experiment comprised swine manure compost (SW) and vermicompost (VE) applied to the soil along with a control treatment (CK). The bacterial community richness decreased after swine manure application and increased after vermicomposting compared to the control treatment. The phage community in the vermicompost-applied soil was dominated (63.1%) by temperate phages. In comparison, the communities of the swine manure compost-applied soil (92.7%) and control treatments (75.4%) were dominated by virulent phages. Phage-encoded carbon sequestration AMGs were detected in all three treatments, with significant enrichment in the vermicompost-applied soil. The average carbon sequestration potential (the coverage ratio of phage AMGs:total genes) of phage AMGs (<i>aceF</i>, <i>GT</i>11, and <i>GT</i>6) in the vermicompost-applied soil (65.18%) was greater than in the swine manure-applied (0) and control soils (50.21%). The results highlight the role of phage-encoded AMGs in improving soil carbon sequestration in vermicompost-applied soil. The findings provide new avenues for increasing soil carbon sequestration.IMPORTANCEThe phage-bacteria interactions have a significant impact on the global carbon cycle. Soil microbial carbon sequestration is a process in combination withcarbon sequestration genes and growth activity. This is the first study aimed at understanding the carbon sequestration potential of phage communities in vermicompost. The results of this study provide variations in carbon sequestration genes in vermicompost microbial communities, and some novel phage auxiliary metabolic genes were revealed to assist bacterial communities to increase soil carbon sequestration potential. Our results highlight the importance of phages in soil carbon sequestration from the perspective of phage-bacterial community interactions.