Gut Microbiota Mediates Host Responses to Microplastic Exposure in Artemia salina

Background: Microplastics, derived from plastic degradation and industrial sources, are widely detected in aquatic environments and food systems, posing increasing environmental and ecological risks. Aims: This study aimed to investigate how microplastics affect host physiology and gut microbiota, as well as determine whether microbiota changes actively modulate host responses. Methods: Using A. salina as a model organism, we combined physiological assays, oxidative stress analysis, gut microbiome profiling, and bacterial functional validation under chronic polystyrene microplastics exposure. Results: Polystyrene microplastics accumulated in the gut and significantly impaired growth and survival, accompanied by reduced digestive enzyme activity and immune function, as well as increased oxidative stress, indicating disruption of physiological homeostasis. Microplastic exposure also induced microbial dysbiosis, characterized by decreased diversity and compositional shifts. Functional assays demonstrated that a bacterium enriched under exposure, Pseudomonas knackmussii, partially restored host growth and physiological functions while reducing oxidative stress. Conclusions: These findings demonstrate that gut microbiota are not only altered by microplastic exposure but also actively modulate host responses to environmental stress, providing new insight into microbiota-mediated resilience under pollutant stress.