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Physiological and molecular responses to different sizes of polystyrene micro/nanoplastics in the model unicellular eukaryote Paramecium tetraurelia
Summary
Researchers exposed single-celled organisms (Paramecium) to polystyrene micro- and nanoplastics of different sizes and found that toxicity increased as particle size decreased. The smallest particles caused the most significant oxidative stress, DNA damage, and disruption to cellular functions including energy metabolism and waste processing. The study provides evidence that nanoplastics pose greater risks to aquatic microorganisms than larger microplastic particles.
The ecological risks of microplastics (MPs) and nanoplastics (NPs) in aquatic ecosystems demand urgent investigation, particularly their molecular-level impacts on microorganisms. This study examines polystyrene micro/nanoplastic (PS-MNP) toxicity using Paramecium tetraurelia, a protozoan model for aquatic toxicology. Through multi-level analyses of cells exposed to PS particles (50 nm, 500 nm, 5 μm), we identified size-dependent toxicity mechanisms. Our findings revealed that PS-MNPs significantly impaired growth kinetics, reducing cell volume and biomass. Physiological assays demonstrated all particles induced ROS surges, activating superoxide dismutase and catalase defenses. Transcriptomic profiling revealed PS-MNPs disrupted DNA repair pathways, induced protein structural damage, and dysregulated energy metabolism networks. Notably, 500 nm particles exhibited maximum toxicity, causing more significant adaptive shift than other sizes. Weighted gene co-expression network analysis (WGCNA) identified three hub genes (pss2, acsf2, tubgcp3) strongly correlated with oxidative damage markers and growth inhibition. These findings demonstrate a size-related toxicity pattern (500 nm > 50 nm > 5 μm) and clarify the impacts of PS-MNPs across phenotypic and molecular levels. The integrated framework advances risk assessment of plastic pollutants, offering mechanistic insights into protistan responses to particulate contaminants.