Toxic effects of tetracycline-adsorbed polystyrene microplastics on E. coli

Microplastics, defined as plastic particles smaller than 5 mm, are pervasive contaminants in aquatic environments. Their high surface area to volume ratio facilitate the adsorption of coexisting pollutants, enabling them to act as carriers for various contaminants, including antibiotics. Antibiotics, widely detected in aquatic environments due to extensive use in medicine and agriculture, may interact with microplastics, thereby altering their distribution and environmental impact. This study investigated the role of polystyrene (PS) microplastics as carriers for tetracycline (TC), a representative antibiotic, and evaluated their toxic effects on Escherichia coli. PS particles with a diameter of 1060 nm were used as model microplastics, and TC was adsorbed onto their surfaces to prepare TC-carrying PS particles. The effects of TC-carrying PS were assessed by examining bacterial growth and viability, with TC and PS alone serving as controls. Exposure to TC-carrying PS resulted in significant decreases in bacterial growth and cell viability in E. coli. Further investigations into the toxicological mechanisms included reactive oxygen species (ROS) generation, lactate dehydrogenase (LDH) release, and malondialdehyde (MDA) levels. Gene expression analyses investigated alterations in pathways related to membrane integrity, oxidative stress response, and DNA repair mechanisms. These findings enhance our understanding of the interplay between microplastics and antibiotics, highlighting the potential ecological risks posed by TC-adsorbed PS microplastics and their implications for environmental health.