Toxic Effects And Molecular Mechanism Of CuO Nps On Euglena Gracilis

Euglena gracilis,also known as Euglena,has an eye-point receptor.It is a kind of eukaryotic single-celled organism.It is spindle-shaped or needle-shaped.Its individual is small,about 100?m.Euglena gracilis can perceive light and use its unique flagellum to exercise.Euglena gracilis is usually distributed in fresh water,especially in a body of water with sufficient light and static,which has stronger vitality.It can be nutritious and natural.Reproduce in water bodies.It has a variety of nutrition modes,including autotrophic,heterotrophic,photoheterotrophic,etc.,and it has richer nutrients when it lives in an autotrophic environment and can be used as a better food source.Euglena gracilis has a short growth cycle,rapid reproduction,and is more sensitive to some poisons,but it is also more adaptable to some substances.It often contains organic pollutants,chemical pollutants,low p H,high salt and high energy ionizing radiation,or it can survive normally in harsh water environments such as wastewater with different carbon sources.It is often used as a model of experimental biology and is easy to separate and cultivate.It can intuitively observe its toxic response from individuals and cells at different levels.Nanomaterials are widely used in industry and scientific research due to their unique mechanical,optical,chemical and electronic processes.According to research reports,the use of nanomaterials is increasing at an exponential rate.Due to the widespread use of nanomaterials and their high radioactivity,nanomaterials must have a certain potential ecotoxicity risk,which over time poses threats to the natural water environment and human health.Cupric oxide powder(CuO NPs)is one of the metal oxides in nanomaterials.It appears frequently in natural water bodies,is more common,and is easy to obtain.Many studies have found that CuO NPs would enter the natural water through various ways,which pose a threat to the balance of the water environment and the health and safety of organisms and even human beings,and destroy the entire ecosystem.Therefore,it is very important to study the toxic effect of CuO NPs on Euglena gracilis,which can effectively evaluate the toxicity of CuO NPs,so as to provide basic theoretical data for the toxic effect of nanomaterials on Euglena gracilis.According to research,there are some data on the toxicity of CuO NPs to microalgae.However,at present,many studies only stay at the level of individual organisms or cells,and relatively few at the molecular level..Therefore,the use of CuO NPs to conduct a more in-depth toxicity study on Euglena gracilis.In this experiment,Euglena gracilis was selected as the model algae species.From the study of CuO NPs on the cell density,growth inhibition rate,ultrastructure,cytochrome chl-a,chl-b and carotenoid content of Euglena gracilis,the influence of CuO NPs on slenderness was analyzed.The influence of Euglena gracilis photosynthesis;The content of antioxidant enzymes MDA,POD and SOD when CuO NPs acts on Euglena gracilis for 144h was measured,and the effect of CuO NPs on the physiological characteristics of Euglena gracilis was analyzed.The transcriptome technology was used to study the effects of CuO nanoparticles on the molecular level of Euglena gracilis.Analyzing the differential gene expression level of Euglena gracilis exposed to 800 mg/L CuO nanoparticles for 144 h,and then explore the GO annotation analysis and KEGG metabolic pathway analysis,and explore the molecular mechanism of CuO nanoparticles on the toxicology of Euglena gracilis.The results are as follows:1.The effects of CuO NPs on the individual level of Euglena gracilis.The concentration of CuO NPs has a negative correlation with the growth of Euglena gracilis,and CuO NPs could inhibit the growth of Euglena gracilis.The higher the concentration of CuO NPs treatment,the greater the growth inhibition rate of Euglena gracilis.The growth of Euglena gracilis showed a short-term low-concentration promotion trend at 24 h.The growth inhibition rate and EC₅₀ of800 mg/L CuO for 144 h were 60.21%and 494.934 mg/L respectively.The toxicity of nano CuO to Euglena gracilis was lower than that of other microalgae.After 800 mg/L CuO NPs treatment for 144h,the morphology of Euglena gracilis cells changed,showing a round state;the morphologies of the chromatophore in the treatment group changed,and the morphologies were blurred and the color became light,which were not easily distinguished from other organelles,and the number of accessory starch grains produced decreased.2.The effects of CuO NPs on the cell level of Euglena gracilis.CuO NPs can significantly reduce the content of Euglena gracilis cytochrome chlorophyll a,chlorophyll b and carotenoids;and inhibit the SOD,POD and MDA content of Euglena gracilis.The concentration of CuO NPs is negatively correlated with the content of Chl-a,Chl-b,carotenoids,SOD,POD and MDA of Euglena gracilis,and the inhibitory effect shows a strong dose-dependent characteristic.3.The effects of CuO NPs on the molecular level of Euglena gracilis.The length of the transcript and Gene sequence is distributed between 301-20961 bp.The average length of Unigene sequence is 1648 bp;N50 is 2055;N90 is 917,and there are 28147 pieces of Unigene spliced.the average length of transcript is 1512 bp;N50 is 1924;N90 is 806,and there are89816 transcripts spliced together.Successfully in the GO database annotation of 16836assigned to the largest number of biological functions,a total of 24,the most number of genes,cell process 9869,assigned to the molecular function of gene has 12 kinds,assigned to the other5 kinds of cell group classification,KOG database successful annotation of 6083 Unigene sequences are classified,can be divided into 24 class function,general function gene of the largest number,a total of 884;The 6039 Unigene gene sequences successfully annotated in KEGG database could be divided into 5 parts,among which the signal transduction function of environmental information processing function was enriched in the largest number and accounted for the largest proportion,with a total number of 641 genes.CuO NPs has a significant effect on the photosynthesis pathway of Euglena gracilis.In the photosynthesis pathway,there are 8 differential genes,and all of them are down-regulated,including Psa A,Psa C,Psb A,Psb D,Psb C,Psb B,beta,and alpha.The FPKM value of the differential gene after CuO NPs treatment,the T2 group was smaller than the control T1 group,the expression was lower,and the photosynthesis ability decreased.