The impact of microplastics on the mice gut microbiome: a meta-analysis.

Microplastics are nearly ubiquitous in the natural environment. There is increasing awareness of the ingestion of microplastics in a wide range of wild animals and humans, but their health and fitness impacts remain poorly understood. Mounting evidence suggests that microplastics could accumulate in the gut, affecting the microbiome and hindering its function. This may constitute a direct pathway through which exposure to microplastics could affect health and disease. However, prior studies on the effects of microplastic exposure on the microbiome show contrasting findings raising the question whether microplastics truly affect the microbiome. Here, we performed the first meta-analysis on the effects of dietary microplastic exposure on the gut microbiome of mice. Overall, we found support for a significant impact of microplastic exposure on the relative abundance of gut bacteria. Microplastic exposure significantly increased the relative abundance of phyla Bacillota and Pseudomonadota. More in depth order-level analysis revealed significant increases in relative abundance within Bacillota of orders Lachnospirales and Lactobacillales and within Pseudomonadota of orders Burkholderiales, Hyphomicrobiales and Moraxellales. In the gut microbiome, Bacillota is associated with carbohydrate metabolism and Pseudomonadota is associated with facultative anaerobes, thus these changes may have functional consequences. Our findings highlight the importance of distinguishing among differing bacterial taxa when assessing the impacts of microplastics on the gut microbiome as the direction and size of the impact varies by phyla.