Microbial-viral synergy in Eisenia fetida gut supports earthworm survival, detoxification, and functional resilience

The ecological success of Eisenia fetida within decomposer food webs is closely linked to the functional diversity of its gut microbiome. This study integrates 16S rRNA gene profiling, whole-metagenome sequencing, and virome analysis to elucidate how microbial and viral communities within the earthworm gut contribute to nutrient biosynthesis, xenobiotic degradation, and environmental adaptation. Earthworms reared on compost feed enriched with Quisqualis indica plant matter showed selective enrichment of bacterial genera such as Ohtaekwangia, Nocardioides, and Steroidobacter, which are associated with hydrocarbon degradation and aromatic compound detoxification. Functional annotation of the gut metagenome revealed complete biosynthetic pathways for riboflavin, lysine, and methionine, and degradation routes for 3-nitropropionic acid (3-NPA) and aromatic pollutants. The gut virome, dominated by Siphoviridae and Myoviridae, carried auxiliary metabolic genes (AMGs) related to redox and xenobiotic metabolism, highlighting viral contributions to microbial adaptability. Reconstruction of metagenome-assembled genomes (MAGs), including a high-quality Flavobacterium MAG encoding both riboflavin biosynthesis and denitrification genes, underscored metabolic specialization within the gut. Collectively, these findings demonstrate that bacterial-viral metabolic synergy underpins E. fetida survival and ecological resilience, suggesting new microbiome-informed strategies for biowaste valorization and soil health restoration through vermicomposting.