Transcriptomics and Metabolomics Revealed the Biological Response of Chlorella pyrenoidesa to Single and Repeated Exposures of AgNPs at Different Concentrations

Abstract

Increased release of engineered nanoparticles (ENPs) from widely used commercial products has threatened environmental health and safety, particularly the repeated exposures to ENPs with relatively low concentration. Herein, we studied the response of Chlorella pyrenoidesa (C. pyrenoidesa) to single and repeated exposures to silver nanoparticles (AgNPs). Repeated exposures to AgNPs promoted chlorophyll a and carotenoid production, and increased silver accumulation, thus enhancing the risk of AgNPs entering the food chain. Notably, the extracellular polymeric substances (EPS) content of the 1-AgNPs and 3-AgNPs groups were dramatically increased by 119.1% and 151.5%, respectively. We found that C. pyrenoidesa cells exposed to AgNPs had several significant alterations in metabolic process and cellular transcription. Most of the genes and metabolites are altered in a dose-dependent manner. Compared with the control group, single exposure had more differential genes and metabolites than repeated exposures. 562, 1341, 4014, 227, 483, and 2409 unigenes were differentially expressed by 1–0.5-AgNPs, 1–5-AgNPs, 1–10-AgNPs, 3–0.5-AgNPs, 3–5-AgNPs, and 3–10-AgNPs treatment groups compared with the control. Metabolomic analyses revealed that AgNPs altered the levels of sugars and amino acids, suggesting that AgNPs reprogrammed carbon/nitrogen metabolism. The changes of genes related to carbohydrate and amino acid metabolism, such as citrate synthase (CS), isocitrate dehydrogenase (IDH1), and malate dehydrogenase (MDH), further supported these results. These findings elucidated the mechanism of biological responses to repeated exposures to AgNPs, providing a new perspective on the risk assessment of nanomaterials.

Mechanisms of photoinduced toxicity of AgNPs to the microalgae Chlorella pyrenoidosa in the presence of hematite nanoparticles: insights from transcriptomics, metabolomics and the photochemical index

“…More information about the AgNPs can be found in our previous studies. 24,31 The hydrodynamic diameters of the AgNPs and HemNPs in the experimental medium, either alone or as a mixture, were determined using a dynamic light scattering (DLS) particle sizer (Malvern Zetasizer Nano ZS90) (Table S1†). The morphology and sizes of NPs in the experimental suspension were further examined by transmission electron microscopy (TEM, JEOL JEM 2100, Japan) (Fig.…”

“…More information about the BG11 medium is provided in our previous study. 24 All glassware and the BG11 medium were autoclaved at 120 °C for 30 min before use. C. pyrenoidesa cells were cultured in an incubator under standard temperature and light conditions, specifically, at a 12 h/12 h daily light/dark cycle with the temperature controlled at 25 ± 1 °C.…”

“…More information about the AgNPs can be found in our previous studies. 24,31 The hydrodynamic diameters of the AgNPs and HemNPs in the experimental medium, either alone or as a mixture, were determined using a dynamic light scattering (DLS) particle sizer (Malvern Zetasizer Nano ZS90) (Table S1…”

“…, sugar metabolism, amino acid metabolism and lipid metabolism) of microalgae at the molecular level. 24 Huang et al also found that low concentrations of AgNPs and Ag + disturbed the antioxidant defense system and nitrogen metabolism of N 2 -fixing cyanobacteria by using metabolomics. 8 Du et al revealed the response of Scenedesmus obliquus to low-dose n C 60 exposure at the molecular level based on transcriptomics and metabolomics, revealing that n C 60 increased the TCA cycle activity and caused feedback inhibition of photosynthesis.…”

“…[21][22][23] Our previous study found that biochemical indicators could not reflect well the effects of AgNPs on microalgae under low-concentration conditions, but the transcriptomics and metabolomics successfully revealed the impacts of AgNPs exposure on the main metabolic pathways (e.g., sugar metabolism, amino acid metabolism and lipid metabolism) of microalgae at the molecular level. 24 Huang et al also found that low concentrations of AgNPs and Ag + disturbed the antioxidant defense system and nitrogen metabolism of N 2 -fixing cyanobacteria by using metabolomics. 8 Du et al revealed the response of Scenedesmus obliquus to low-dose nC 60 exposure at the molecular level based on transcriptomics and metabolomics, revealing that nC 60 increased the TCA cycle activity and caused feedback inhibition of photosynthesis.…”