| Due to the long-term abuse of antibiotics in aquaculture and animal husbandry,the ecological toxic effects of the ecological environment have caused widespread concern.In this study,three kinds of ciliates were chose as experimental subjects,to study two widely used tetracycline?TC?and tetracycline hydrochloride?HTC?on the acute lethal effects,and the growth curve effects of monoclonal lines,the activities of superoxide dismutase?SOD?,peroxidase?POD?,hydrogen peroxidase?CAT?and the ultrastructural changes of ciliates under the lowest observed effect concentration of two antibiotics.The results showed that lethal concentration 50%(24h-LC50)of Teracycline to Stylonychia lemnae?Paramecium caudatum and Stentor coeruleus was171.02516mg·L-1?52.36125mg·L-1?199.35632 mg·L-1;Lowest observed effect concentration?24h-LOEC?is 65.16884mg·L-1?15.19917mg·L-1?139.37022mg·L-1;concentration for 50%of maximal effect(24h-EC50)is 40.06268mg·L-1?9.12158mg·L-1?94.35393mg·L-1.24h-LC50 of Tetracycline Hydrochloride to Stylonychia lemnae?Paramecium caudatum and Stentor coeruleus is 44.48566mg·L-1?50.24583mg·L-1?3.77769mg·L-1;24h-LOEC is 20.03134mg·L-1?24.67175mg·L-1?13.44498mg·L-1;24h-EC50 is 13.97623mg·L-1?12.78439mg·L-1?8.39073mg·L-1.The results of monoclonal growth curve effects of three ciliates were measured at the 24h-LOEC concentration of two tetracycline antibiotics show that two kinds of tetracycline antibiotics have significant inhibitory effects on the growth and reproduction of three ciliates.The growth rate decreased and the top number of propagated individuals decreased.Three antioxidant enzyme activities show that the activities of SOD,POD and CAT in the three ciliates were inhibited by with tetracycline and tetracycline hydrochloride.Among them,two kinds of tetracycline antibiotics have stronger effects on POD enzyme activity than,CAT enzyme and SOD enzyme.By TEM obeserration,We found that two kinds of tetracycline antibiotics have a destructive effect on the mitochondria of Stylonychia lemnae?Paramecium caudatum and nuclear of Stentor coeruleus.Addition,tetracycline and tetracycline hydrochloride reduced the cytoplasmic dense part of the Stylonychia lemnae and Stentor coeruleus,and there are large number of vacuolar structures emerged in the cytoplasm.In summary,this study found that tetracycline and tetracycline hydrochloride has acute and chronic toxic effects on single cell organisms.Higher concentrations of tetracycline antibiotics within 24 hours can cause protozoan ciliate to death.The lower concentration of tetracycline antibiotics have a significant effect on the ultrastructure of the important organelles of ciliates and the physiological metabolism of cells.So they interfere with cell's normal growth and reproduction,causing changes of the microbial community.Therefore,it is necessary to sive strict environmental emission standards and carry out early prediction and early warning studies on the environmental risks of such microbiological organisms to effectively control the impact of tetracycline antibiotics on ecosystems. |
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