Earthworm Gut Microbiota as a Biological Driver of Plastic Degradation: Implications for Microplastic Mitigation

Microplastic pollution in terrestrial environments has emerged as a growing threat to agricultural sustainability. Earthworms and their gut microbiota have recently attracted attention as potential nature-based agents for microplastic mitigation. This study systematically synthesizes empirical evidence on the role of earthworm intestinal microorganisms in the transformation and potential biodegradation of microplastics. A literature synthesis was conducted using Scopus-indexed, peer-reviewed publications published between 2018 and 2025 that examined interactions among microplastics, earthworms, and gut microbiota. The synthesis indicates that microplastic degradation within the earthworm digestive system is a multifactorial process involving mechanical fragmentation, selective microbial enrichment, and biological and metabolic activity. Across different earthworm species and polymer types, the phyla Actinobacteria, Proteobacteria, and Firmicutes consistently dominated the gut microbiome. Several genera, including Bacillus, Paenibacillus, Rhodococcus and Streptomyces, were repeatedly associated with microplastic transformation. Earthworm activity may also improve nutrient availability, stabilize soil microbial communities and enhance plant tolerance to microplastic-induced stress. However, major gaps remain in quantifying biodegradation rates, determining microbial removal efficiency and identifying enzymes directly involved in plastic degradation. Overall, this synthesis positions vermiremediation as a promising strategy for managing terrestrial microplastic contamination, while underscoring the need for stronger mechanistic evidence to support practical application.