Critical Ecological Niche in Soil Carbon Cycling and Environmental Remediation: The Gut Microbiota of Earthworms Pheretima aspergillum

The gut microbiota of earthworms plays a crucial role in the carbon cycle and pollution remediation. However, degradation capacities and strategies of earthworm gut microbiota towards major carbon source. We selected endogeic earthworm Pheretima aspergillum (E. Perrier, 1872) from the surface layer (0–10 cm depth) of Hortic Anthrosol soil and conducted metagenomic analyses of gut microbiota, casts, and habitat soil. The α-diversity indexes of earthworm P. aspergillum gut microbiota were higher than those of cast and soil, indicating a more diverse community structure in earthworm P. aspergillum gut. Gut microbiota composition differed markedly from casts and soil, with Actinomycetota and Bacillota enriched in earthworm guts. The phyla of Actinomycetota and Bacillota were enriched in earthworm gut microbiota. Furthermore, Methylococcaceae and Methanosarcinaceae families (methane cycling) were enriched in earthworm gut microbiota. Soil bacterial communities exhibited greater degradation potential for starch, cellulose, xylan and pectin, whereas gut microbiota showed superior chitin degradation capacity. Metagenomic analysis of the earthworm gut microbiota revealed the presence of several genes associated with plastic degradation. Therefore, we speculate that the microbial community may harbor the potential to degrade microplastics. These findings elucidate earthworms’ role in soil carbon cycling and remediation.