Evaluation of the physiological response of Chlorella vulgaris to nanoplastics: involvement of boron and the amino acid biosynthesis pathway

Abstract

The environmental impact and toxicity analysis of polystyrene nanoplastics (PSNPs) have become active areas of research worldwide. In this study, Chlorella vulgaris (Chlorella) was used as the experimental material, and the effects of 100 nm, 300 nm and 500 nm PSNPs on the chlorophyll fluorescence, ion group profile and secondary metabolisms of Chlorella were analyzed by fluorescence analyzer, ICP-MS and GC-MS. PSNP exposure significantly reduced chlorophyll a and b fluorescence by 6.6% and 24.1%, respectively. The chlorophyll fluorescence parameter Y(NO) significantly increased 1.05-fold, while ETR and Y(Ⅱ) significantly decreased by 1.6–2.9% and 1.8–2.9%, respectively. The ion group profiles varied significantly, which was T1 > T2 > T3. Boron (B) serving as the key driving force of metabolic network response changes. Chlorella uses excitatory regulation of basic metabolic networks to balance PSNP damage. A total of 362 metabolites were isolated and identified by GC-MS. The induced differentially expressed metabolites (DEMs) were mainly organic acids and derivatives, and the key biomarkers were (r)− 3-hydroxybutyric acid, o-phosphoserine, and galactinol. The key response metabolic pathway was amino acid biosynthesis, aminoacyl-tRNA biosynthesis, and valine, leucine, and isoleucine biosynthesis. Overall, the key factors in the physiological response of Chlorella to PSNPs were B and the amino acid biosynthesis pathway. These findings provide new insight into the response of aquatic plants to PSNP exposure and will help to guide the ecological risk assessment of PSNP exposure.