氨化菌分离鉴定及其对草甘膦-镉的联合毒性响应

Ammonifying Bacteria and Their Toxic Response to Combined Pollution of Glyphosate and Cadmium:Isolation and Identification

文章为考察环境中典型污染物农药与重金属复合污染物对生态环境的影响,选取氨化菌这一自然界中的常见菌种作为实验对象,以种植土壤作为菌源,分离筛选得到一株氨化菌(Z1)。经鉴定,菌株Z1为假单胞菌属,12 h氨化速率可达0.792 mg/(L·h),48 h氨氮生成量达到22.500 mg/L。以草甘膦(GLY)和重金属镉(Cd)为目标污染物,应用直接均分射线法设计二元混合物体系,运用时间毒性微板分析法系统测定GLY、Cd及其二元混合物体系对氨化菌Z1在不同暴露时间的浓度-效应数据,应用拟合归零法分析GLY-Cd混合物组分间的相互作用类型及强度。结果表明,单个污染物对Z1的毒性随浓度升高逐渐增强,具有浓度和时间依赖毒性,且Cd对Z1的毒性始终大于GLY。GLY-Cd混合物体系的5条射线(R1~R5)具有浓度、时间和组分比依赖毒性,毒性相互作用主要表现为拮抗作用,其中R3在第8小时dCA值最大,可达65.4%,GLY与Cd的复合污染使得它们在土壤中的毒性和生物利用度有所降低。

In order to investigate the effects of combined contamination of the typical pollutants,such as pesticides and heavy metals,on the ecological environment,the ammonifying bacteria,a common strain in nature,was selected as an experimental study object.The experiment was conducted with cultivated soil as the bacterial source,a strain of ammoniated bacteria(Z1)was isolated and screened,which was identified as Pseudomonas.It was showed that the ammonification rate reached 0.792 mg/(L·h)at 12 h,and the amount of ammonia nitrogen produced was up to 22.500 mg/L at 48 h.In the case of glyphosate(GLY)and heavy metal cadmium(Cd)being used as target pollutants,the binary mixture system(GLY plus Cd)was thereby designed by the direct equipartition ray method;by adopting the time-dependent toxicity microplate analysis method,the efffects of GLY,Cd and the binary mixture system on Z1 were respectively determined about the concentration-effect data at different exposure time;and toxicity interaction type and intensity of the components of GLY-Cd mixture were analyzed by fitting zeroing method.As a result of the experimntal study,the toxicity of a single pollutant to Z1 gradually increased as its concentration went up,with the characteristics of concentration and time dependent toxicity.The toxicity of Cd to Z1 was always greater than GLY to Z1;the five rays(from R1 to R5)of the GLY-Cd mixture system were characterized with dependent toxicity in terms of concentration,time and component-ratio,and the toxicity interaction mainly appeared to be antagonism,and R3 had the highest dCA value(65.4%)at 8 h.In summary,the combined pollution of GLY and Cd reduced their toxicity and bio-availability in soil.