Toxic Response And Molecular Mechanism Of Three Antibiotics To Paramecium Caudatum And IBR Assessment

The large-scale use of antibiotics leads to the continuous increase of the content in the water environment,and a large amount of antibiotic pollution will cause certain harm to aquatic organisms.In this study,three antibiotics,sulfamethoxazole,tetracycline and levofloxacin,were used to stress paramecia for 24 hours,to detect the gene expression of biomarkers and related enzyme activities,and to analyze the mechanism of Paramecium caudatum at the molecular,physiological and biochemical levels.Using IBR to analyze the evaluation of antibiotic toxicity of Paramecia in surface water concentration,several major biomarkers were screened for future evaluation.The specific results are as follows:1.Response of 8 biomarkers of Paramecium caudatum to antibioticsThe effects of antibiotics on the physiological level of Paramecium caudatum were analyzed by changing the 8 biomarkers of paramecia in the environmental concentration range of three antibiotics.The experimental results showed that oxidative stress damage was induced by the three antibiotics.Among them,two biomarkers,MDA and GSH-Px,were more sensitive under different concentrations of antibiotics.SOD and CAT enzymes were mainly promoted,and MDA content,GSH-Px and PGK enzyme activities were inhibited.2.Response mechanism of six enzyme genes of Paramecium caudatum to antibioticsBy studying the changes of gene expression levels of six enzymes in Paramecium caudatum under three antibiotic stresses,and analyzing the correlation between enzyme activity and gene expression,exploring the molecular response mechanism of Paramecium caudatum to antibiotics.The results showed that the gene expressions of SOD,GSH-Px and PGK were inhibited under the stress of three antibiotics.CAT,CYP450 and ATPase gene expression was up-regulated;the enzyme activities of SOD,GSH-Px and PGK were relatively consistent with the gene expression trends,the changing trends of CAT,CYP450 and ATPase activity and enzyme gene expression were roughly opposite.There were positive and negative cross-relationships among the six enzyme genes under different antibiotic treatments.Under sulfamethoxazole treatment,the gene expression levels of CAT and ATPase were more correlated with other enzyme genes.There were many correlations among antioxidant enzymes under tetracycline stress.Under levofloxacin stress,SOD and CAT gene expression levels were more correlated with other enzyme genes.Under sulfamethoxazole treatment,PGK gene expression and ATPase activity were more correlated with other enzymes and genes.Under tetracycline treatment,CAT activity was more correlated with other enzymes and genes.Under levofloxacin treatment,SOD,ATPase,PGK and CYP450 enzyme gene expression levels were more cross-correlated,and PGK and GSH-Px enzyme activities were more cross-correlated than other enzymes.3.IBR comprehensively evaluates the toxic effects of three antibioticsThrough the correlation and IBR analysis of 8 biomarkers and concentrations of Paramecium caudatum under the stress of three antibiotics,it was revealed that each antibiotic has a corresponding combination of different biomarkers under different concentrations.These combinations can be used to evaluate antibiotic contamination in surface water,which is an effective means of antibiotic environmental toxicity monitoring.According to the evaluation of the IBR index,the toxic effects of the three antibiotics were ranked in descending order of levofloxacin > sulfamethoxazole >tetracycline.