Impact of microplastics exposure on the reconfiguration of viral community structure and disruption of ecological functions in the digestive gland of Mytilus coruscus.

Microplastics (MPs) pose ecological risks by serving as viral vectors and disrupting host microbiomes. This study investigated the impact of MPs on the digestive gland virome of Mytilus coruscus through an in situ exposure experiment on Xixuan Island, Zhoushan, China, using polyethylene MPs and metagenomic sequencing. MPs biofilms were dominated by lytic viruses (> 99 %) with low diversity (Shannon index = 4.10 ± 0.39), whereas digestive glands harbored a more diverse virome (Shannon index = 7.26 ± 1.26). MPs ingestion significantly reduced virome diversity and altered viral community composition. Functional analysis showed that MPs biofilms were enriched in genes related to genetic processing, carbohydrate metabolism and membrane biogenesis, while transcription- and replication-related genes declined (P < 0.05) in digestive glands post-ingestion. MPs biofilms carried abundant antibiotic resistance genes (ARGs) and virulence factors, selectively enriching multidrug resistance genes (efrA, patB) while reducing functional viral gene abundance. Metal (Zn, Hg, As) and biocide resistance genes were prevalent in MPs biofilms but declined post-ingestion. Additionally, MPs ingestion weakened microbial network stability, potentially impairing immune regulation and metabolic homeostasis. These findings underscore MPs' role in shaping viral communities and spreading resistance genes, heightening ecological risks in marine environments.