Proteomic insights into composition-dependent effects of microplastics on freshwater microalgae Chlamydomonas reinhardtii

The widespread presence of microplastics (MPs) in freshwater systems has raised concerns about their potential ecotoxicity on aquatic organisms. In this study, we evaluated the effects of four MPs with different compositions, namely polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and polypropylene (PP), on freshwater microalgae Chlamydomonas reinhardtii. PS and PVC MPs caused greater growth inhibition and stronger oxidative stress response than PP and PE MPs. Proteomics analysis was employed to explore the mechanical understanding of the composition-dependent toxicity of MPs on microalgae. Proteins involved in photosynthesis processes were identified as contributors to the diverse responses of microalgae to differently composed MPs. Photosynthesis activity of algae, including pigment content and photoprotective response, was determined to reflect the distinct effect of the four MPs. The indicated down-regulated expression of photosynthetic proteins by proteomics analysis was further confirmed using western blot, with PVC and PS showing greater impacts on their expression reduction. Our findings not only show the composition-dependent effect of MPs on microalgae but also provide important insights into the molecular mechanism of MPs’ toxicity on natural phytoplankton species.

微塑料（MPs）在淡水系统中的广泛存在引发了人们对其对水生生物潜在生态毒性的担忧。本研究评估了四种不同成分的微塑料——聚乙烯（PE）、聚苯乙烯（PS）、聚氯乙烯（PVC）和聚丙烯（PP）——对淡水微藻莱茵衣藻（Chlamydomonas reinhardtii）的影响。PS和PVC微塑料对莱茵衣藻的生长抑制作用及氧化应激反应强度均高于PP和PE微塑料。通过蛋白质组学分析，探究微塑料成分依赖性毒性对微藻作用的分子机制。参与光合作用过程的蛋白质被鉴定为微藻对不同成分微塑料产生差异响应的关键因素。通过测定藻类的光合作用活性（包括色素含量和光保护响应），以反映四种微塑料的不同影响。蛋白质组学分析显示的光合蛋白表达下调现象，经蛋白质印迹法（western blot）进一步验证，其中PVC和PS对光合蛋白表达降低的影响更为显著。本研究结果不仅揭示了微塑料对微藻的成分依赖性效应，还为理解微塑料对天然浮游植物物种毒性的分子机制提供了重要见解。