Research On The Toxicity Of Three Antibiotics To Two Ciliates

The extensive use of antibiotics in manufacture and life has made it a new type of environmental pollutant.In order to study the environmental toxicity of antibiotics,this paper selected Paramecium caudatum sensitive to antibiotic stress and Colpoda inflata tolerant to antibiotic stress as experimental objects.The acute toxicity effect,population effect,physiological toxicity and molecular toxicity of three antibiotics including sulfamethoxazole?SMZ?,tetracycline?TC?and levofloxacin?LEV?widely used on two ciliates have been studied.The conclusions were as following:1.The acute toxicity parameter indexes of three antibiotics were obtainedThe 24h half inhibitory concentration?EC50?of SMZ on Paramecium caudatum and Colpoda inflata was 46.0934 mg·L-1 and 74.6704 mg·L-1,respectively.The maximum no-effect concentration?NOEC?was 33.6.67 mg·L-1 and 50.3185 mg·L-1,respectively.The half of the lethal concentrations?LC50?were 155.6268 mg·L-1and691.0391 mg·L-1,respectively.And the lowest influential concentrations?LOEC?were 129.3425 mg·L-1 and 358.3654 mg·L-1,respectively.The 24 h half inhibitory concentration?EC50?of LEV on Paramecium caudatum and Colpoda inflata were 6.9214 mg·L-1 and 14.4108 mg·L-1,respectively.The maximum no-effect concentration?NOEC?were 4.6549 mg·L-1 and 8.6312 mg·L-1,respectively.The half of the lethal concentrations?LC50?were 14.8612 mg·L-1and27.7201 mg·L-1,respectively.And the lowest influential concentrations?LOEC?were 12.3064 mg·L^-11 and 22.4602 mg·L^-1,respectively.The 24h half inhibitory concentration(EC₅₀)of TC on Paramecium caudatums and Colpoda inflata were 12.6523 mg·L^-11 and 73.4685 mg·L^-1,respectively.The maximum no-effect concentration?NOEC?were 5.0625 mg·L^-11 and 49.5707 mg·L^-1,respectively.The half lethal concentration(LC₅₀)were 48.2237 mg·L^-11 and 125.3343mg·L^-1,respectively.And the lowest affected concentration?LOEC?were 22.9082mg·L^-11 and 110.4547 mg·L^-1.2.The effects of three antibiotics on the population growth of ciliates were detectedUnder the treatment of the concentration of EC₅₀,the 11-day monoclonal growth curves of Paramecium caudatums was significantly inhibited.Under the treatment of three antibiotics,the maximum population density of Paramecium caudatums were 38,20 and 32,respectively,which were significantly lower than that of the control group,121.The inhibition effect were same,the exponential growth period and the plateau period were shortened into the early decline period.According to the 14-day monoclonal growth curves of Colpoda inflata,SMZ greatly promoted the division of Colpoda inflata,the exponential growth period was prolonged,and the maximum population density was 1600,which was higher than that of the control group,1200.However,LEV and TC significantly inhibited the division of Colpoda inflata,and the maximum population density were 500 and 720,respectively,lower than that of the control group.The index growth period and the plateau period were shortened.3.The responses of antioxidant enzymes and degrading enzymes to three antibiotics were analyzedTwo ciliates were under the concentrations of EC50 of three antibiotics for 24 h,48 h and 72 h.The physiological level and the genetic level of the enzymes of ciliates were examined.The activity of enzymes at the physiological level were as follows:SuPeroxide dismutase?SOD?of two ciliates were significantly inhibited,and the inhibition effect increased with the extension of the treatment time.There were differences in activity of Glutathione peroxidase?GPX?of two ciliates.The activity of GPX of Paramecium caudatum showed a downward trend with the extension of the treatment time and eventually,it was significantly lower than that of the control group.The activity of GPX of Colpoda inflata showed a downward trend under the treatment of TC,but there were upward trend under SMZ and LEV and finally they were higher than that of the control group.The degradation enzyme Lignin Peroxidase?LiP?was significantly promoted with the extension of the treatment time.The changes of activity of Laccase?Lac?were different.Paramecium caudatum showed increase first and then decreased,but Colpoda inflata showed a gradually increasing trend.4.RT-qPCR was used to analyze the expression of enzyme-related genes under the stress of three antibioticsFour enzyme-related genes of two ciliates changed significantly in different periods.The enzyme-related genes of SOD and LiP were highly consistent with the change of enzyme activity.However,the trends of enzyme-related genes of GPX and Lac were different from that of enzyme activity.