Gut-Microbial Responses to Acute Polyester Microplastic Exposure in Zebrafish: Dysbiosis, Opportunistic Bacteria, and Functional Impact.

Microplastics are widespread environmental contaminants with adverse health impacts. The gastrointestinal tract represents a primary site for host-microplastic contact and interactions, but microplastic-driven perturbations of the gut microbiome and how they mediate toxicity to the gut and host's health remain poorly elucidated. In this study, zebrafish (Danio rerio) were exposed to environmentally ubiquitous polyester microplastics and investigated for acute dysbiosis and host-microbiome molecular responses using an integrated histological and multi-omics approach. Gut transcriptomic results first revealed initial dysregulations under microplastic stress, increasing energy-metabolic activity and suppressing detoxification-associated pathways on day 3, followed by downregulated gut epithelial maintenance and anti-inflammatory responses by day 7. During this process, opportunistic bacterial taxa such as Edwardsiella and the microbial antioxidant biosynthesis pathway can be enriched transiently. The limited structural damage and modest microbiome alterations observed after acute exposure, however, may suggest partial resilience of the host gut and microbiome. This study demonstrates microplastic-induced gut impairment and host-microbiome responses to acute polyester microplastic stress, providing evidence to enable better characterization of the gut health risks associated with microplastic contamination.