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Dynamic Uptake and Elimination of Microplastics by Tetrahymena thermophila
Summary
Scientists tracked how a single-celled freshwater organism absorbs and gets rid of microplastics, finding that cells take in plastic particles quickly within the first hour, but levels drop afterward, mostly because the cells divide and "dilute" the plastic between daughter cells rather than actually eliminating it. This matters because these tiny organisms sit at the bottom of the food chain, meaning the microplastics they build up could pass up the chain to fish and eventually to the food we eat, making this research a key step toward understanding how plastic pollution moves through ecosystems and potentially into our diets.
Understanding the fate and impacts of microplastics (MPs) on foundational organisms within food webs is essential for accurately assessing their toxicity and environmental risks. While the accumulation and toxicity of MPs in organisms at low trophic levels have been documented, the analysis of the absolute cellular uptake of MPs at a single-cell level with high-throughput methods remains a challenge. In this study, we developed a flow cytometry-based approach integrating a particle balance method and biokinetic modeling to quantitatively assess the uptake and elimination dynamics of fluorescently labeled MPs in the freshwater ciliate . The intracellular accumulation of MPs was calculated by subtracting the extracellular MPs from the total exposure amount, ensuring that the measurement was free from interference caused by fluorescence quenching or cellular background noise. Our results revealed that intracellular MPs continuously increased during the first hour, followed by a marked decline within 24 h. By applying a biokinetic model, we demonstrated that the effect of cell division on reducing MP burden is 3.6 to 5.8 times greater than that of elimination, depending on the exposure concentration. The calculated bioconcentration factors (BCFs) exceed 4800, indicating a significant potential for bioaccumulation of MPs in . These results enhance our understanding of the initial processes through which MPs enter the food chain and provide essential technical support for further research on the quantitative toxicity assessment of MP pollution.