3种重金属对蛋白核小球藻的联合毒性及机理

Combined Toxicity and the Mechanisms of Three Heavy Metals to Chlorella pyrenoidosa

重金属污染日益严重,对人类具有潜在威胁。该文以绿藻蛋白核小球藻(Chlorella pyrenoidosa)为受试生物,3种典型重金属污染物镉(Cd)、铜(Cu)和铬(Cr)为研究对象,采用均匀设计射线法设计重金属三元混合物体系(Cd-Cu-Cr),应用时间毒性微板分析法系统考察3种重金属对蛋白核小球藻的单一毒性及联合毒性,并通过分析绿藻中叶绿素和蛋白质含量探讨3种重金属及其混合物的可能的毒性作用机理。结果表明:3种重金属对蛋白核小球藻的毒性均随着暴露时间的延长逐渐增强,呈现明显的时间依赖性;重金属处理后的蛋白核小球藻中叶绿素含量随暴露时间的延长不断减少,如在24~72 h时,Cd处理的蛋白核小球藻中的叶绿素减少率增长较快,后趋于稳定,而Cr和Cu处理后的绿藻在整个暴露时间内叶绿素减少率均增加;Cd和Cr处理后绿藻的蛋白质含量减少率随着暴露时间的延长快速增加,而Cu处理后的绿藻中蛋白质减少率在24~72 h趋于平缓,之后减少率迅速增加;5条混合物射线的毒性均为加和作用,即组分间没有发生明显的毒性相互作用;三元混合物在低浓度时对蛋白核小球藻具有促进生长作用,在高浓度时抑制其生长,即Hormesis现象;三元混合体系处理后的绿藻中叶绿素及蛋白质的含量与单一Cu处理后的变化规律相似,这表明混合物的毒性机制受单一组分的影响。

Heavy metal pollution is becoming more and more serious,which has a potential threat to human beings.Selecting green algae Chlorella pyrenoidosa(C.pyrenoidosa)as the experimental organism and three typical heavy metal pollutants including cadmium(Cd),copper(Cu)and chromium(Cr)as the research objects,the single and combined toxicity of three heavy metals to Chlorella pyrenoidosa were systematically investigated by time toxicity microplate analysis.The heavy metal ternary mixture system(Cd-Cu-Cr)was designed by the uniform design ray method.The possible toxicity mechanism of three heavy metals and their mixtures was studied by analyzing chlorophyll content and protein content in green alga.The results showed that the toxicity of three heavy metals to C.pyrenoidosa increased gradually with the increase of exposure time,showing obvious time-dependence.After heavy metal treatment,the chlorophyll content of C.pyrenoidosa decreased continuously with the exposure time.During 24-72 h,the chlorophyll reduction rate increased rapidly in C.pyrenoidosa treated by Cd,then tended to be stable,but the chlorophyll reduction rate of green algae treated by Cr and Cu increased rapidly during the whole exposure time.After the treatment of Cd and Cr,the decrease rate of protein content increased rapidly with the prolongation of exposure time.However,after the treatment of Cu,the protein reduction rate in green algae tended to be gentle in24-72 h,and then increased rapidly.According to CA,all of the five mixture rays exhibited additive action,that is,there is no obvious toxic interaction within mixtures.The ternary mixture could promote the growth of C.pyrenoidosa at low concentration and inhibit the growth at high concentration,showing hormesis phenomenon.The content of chlorophyll and protein in green algae treated by ternary mixture system was similar to that of treatment of single Cu,which indicated that the toxicity mechanism of the mixtures was affected by a single component.