Multiple perspectives assess the ecotoxicological effects of polystyrene microplastics on Eisenia fetida

Herein, we aimed to study the role of gut bacteria in PS-MPs-induced gut barrier dysfunction to clarify the potential mechanism of action. First, PS-MPs exposure caused gut barrier damage of Eisenia fetida, comprised of obvious injured of gut epithelial cells, and significantly lower transcription levels of the gut tight junction (TJ)-related protein genes. We observed significantly increased bacterial lipopolysaccharide (LPS) levels and gut bacterial load, indicating gut bacterial translocation occurred that might result from gut barrier damage. Subsequently, antibacterial immune responses were activated. The gut barrier damage could weaken host selective pressures (deterministic process) on gut bacteria, such as particular pathogens. Indeed, some members in Proteobacteria, e.g., Aeromonas and Escherichia/Shigella, considered potential opportunistic pathogens, were gut bacterial signatures of PS-MPs exposure groups. And most of these bacterial OTUs were pivotal contributors to gut TJ and gut bacterial translocation, indicating gut bacteria involved in PS-MPs-induced gut toxicity.