Toxic Effects Of Sulfadiazine On Selenastrum Capricornutum

While antibiotics are widely used in medical,animal husbandry and aquaculture industries,they also cause serious harm to the environment.Sulfonamides antibiotics are a class of commonly used antibiotics,which have some advantages like low cost and wide antibacterial spectrum.However,the abuse of antibiotics and other irrational used behaviors,sulfonamides accumulated in large quantities in water,which seriously threatens the living environment of aquatic animals and plants,and even endangers human health through enrichment in the food chain.In this paper,sulfadiazine was taken as the research object,and the toxic effect of sulfadiazine on Selenastrum capricornutum will be studied to analyze the toxic mode and mechanism,so as to provide basic information for subsequent treatment of antibiotic pollution.In this experiment,six concentrations(0,10,20,30,40,50 mg/L)were set and exposed for 9 days.Some different toxic effects of sulfadiazine at different concentrations on Selenastrum capricornutum like cell morphology,antioxidant activity,membrane permeability and photosynthesis were be studied.The results were as follows:(1)Sulfadiazine had a time-concentration effect on the growth inhibition of Selenastrum capricornutum.When the concentration of sulfadiazine was?10 mg/L,the density of algal cells decreased significantly,the algal fluid lost greenness and deposited to the bottom of the bottle.Under 50 mg/L sulfadiazine stress,the Selenastrum capricornutum turns yellow and produces flocculents.(2)Under the stress of low concentration(?20mg/L),SOD and POD had no significant changes.However,when the concentration of sulfadiazine was greater than or equal to 30mg/L,the activities of antioxidant enzymes SOD and POD decreased significantly,and a large amount of intracellular reactive oxygen species was accumulated.(3)When the concentration of sulfadiazine was more than 20 mg/L,the content of soluble protein(SP)in algae cells decreased significantly;When the concentration of sulfadiazine ?10 mg/L,the soluble sugar content decreased significantly,that means the cell membrane is damaged.(4)When the concentration of sulfadiazine ?10 mg/L,the chlorophyll fluorescence parameters did not significantly decrease,indicating that the low concentration of SD had no significant toxicity to PSII.When the concentration of sulfadiazine ?10 mg/L,the content of photosynthetic pigment in the cells of Selenastrum capricornutum was significantly decreased,the photochemical reaction was inhibited,and the photosynthesis was seriously weakenedIn conclusion,Selenastrum capricornutum is sensitive to the toxicity of sulfadiazine,mainly through inhibiting the synthesis of tetrahydrofolate to destroy cell membrane system and chloroplast,the osmotic balance of cells is disrupted,resulting cells lack of enough material and energy,and eventually make the cells death.Selenastrum capricornutum can be used as a model organism to evaluate the content of sulfadiazine in water and provide scientific basis for ecological risk assessment of sulfadiazine.