The Molecular Ecotoxicity Of Emerging Pollutants On Tetrahymena Thermophila

Kinds of emerging pollutants release to the water environment continuously as people daily life, will cause "pseudo-persistent" pollution, and lead to the damages on ecological environment and human health cannot be ignored.In this study, Antibacterial agents (Triclosan,Triclocarban),Cephalosporins (cephalexin, cephradine) and Tetracycline Antibiotics (tetracycline,oxytetracycline,Aureomycin) were selected as the target compounds to determine their single toxicity and mixture effect on Tetrahymena thermophila. The activity of lysosomes and membrane function were measured using fluorescent dyes as indicators; The morphological structure of cells were observed which exposed to different compounds with fluorescence microscopy and Synchrotron radiation X microscope; The enzyme activity of cells were researched at environmentally relevant concentration.(1) The results showed that the growth of Tetrahymena have been both inhibited significantly by theμg·L-1 level of TCS and TCC. The 24 h-EC50 of TCS and TCC were 141μg·L-1 and 728μg·L-1. The growth of Tetrahymena have also been inhibited significantly by the mg·L-1 level of Tetracycline Antibiotics. The 24 h-EC50 of tetracycline and chlortetracycline were 103.89 mg·L-1,53.73 mg·L-1. Surprisely, the growth of Tetrahymena have no significant effect exposed to oxytetracycline. When the concentration reach to 200 mg·L-1, the inhibition of growth is just 62.87%. There have no significant effect exposed to low dose of cephalexin and cephradine. When the concentration of cephalexin reached 200 mg·L-1, the growth stimulation is 288.94%. There have no significant effect exposed to Ceftriaxone and 7-ACA.(2)When the concentrations of TCS and TCC reached 1000μg·L-1, the obvious damages of cell membrane were observed. Also, the activity of lysosomes were reduced to 88.63% and 95.75% of control fluorescence values, respectively, when the cells were exposed to 1μg·L-1 of TCS and TCC for 2 h. When the concentration of tetracycline reached 1mg·L-1, the cell membrane were damaged obvious and the activity of lysosomes were reduced significantly. Cephalexin in the range of mesured concentration has obvious effect of "protection" to the cell membrane and the activity of lysosomes. When the concentration of cephradine reached 200mg·L-1 the activity of lysosomes were reduced significantly.(3) The obvious changes of cell stucture were observed using fluorescence microscopy, when the cell exposed to TCS and TCC. Cells decrescent and damaged easily, the activity of cells became weakly.(4) The results of the enzyme activity showed that, When the exposure level was set at 1.0μg.L-1, TCS stimulated the SOD enzyme activities significantly(P<0.05), than the content of MDA is reduced remarkly(P<0.05), also stimulated the activities of GST,CAT and ATPase(P<0.05), at the same time a significant reduction in LDH was found(P<0.05). However, TCC showed no significant change in GST,CAT and ATPase activity, a significant reduction in LDH and MDA were found(P<0.05). When the exposure level was set at 1.0μg.L-1, both cephalexin and cephradine could stimulate SOD activities (P<0.05) and reduce LDH activities (P<0.05) of Tetrahymena.(5) The results of mixture effect tests showed that, mixture of TCS and cephalexin, cephradine had additive effect. Mixture of TCS and TCC, tetracycline, chlortetracycline had synergistic, additive, antagonistic effect, respectively.(6) The ecological risk assessment further indicates that more attention should be paid to the ecological toxic effects of emerging pollutants at the environmental relevant concentration.