The Response Mechanisim Research Of Heavy Metal Cadmium On Colpoda Inflata

Cadmium is an important pollutant for soil prevention and control,with the increasing content of cadmium in soil because of industrial activities,and it can be accumulated in crops and lead great harm to human health.The dominant protozoa Colpoda inflata has screened in the black soil of northeast China in this study;The acute toxic effect of heavy metal cadmium on Colpoda inflata was explored;The molecular,cellular,physiological and biochemical response mechanisms of Colpoda inflata on cadmium under 96h-LC₅₀ and 96-EC₅₀ were analyzed;and the evaluation indexes of cadmium environmental toxicity on Colpoda inflata were analyzed by IBR method.The specific results are as follows:1.Colpoda inflata have been selected as the dominant protozoa in the black soil of northeast China.Colpoda inflata belongs to the dominant species of soil protozoa,and its evolution mode is"polygenesis".Through morphological observation and phylogenetic analysis,it is identified as Colpoda inflata belonging to the Harbin population.2.Acute toxic effects of cadmium on Colpoda inflata.The values of LC₅₀ and LOEC of Colpoda inflata on cadmium were the lowest at 24hours,and the concentration of these two parameters increased with the extension of exposure time.The values of EC₅₀ and NOEC of Colpoda inflata on cadmium were the lowest at 48 hours,and the fission of Colpoda inflata was obviously inhibited by cadmium.Compared with the toxicity standard of new chemical substances,the toxicity intensity of cadmium in Colpoda inflata was highly toxic.3.The response mechanism of Colpoda inflata on cadmium.The oxidative stress of Colpoda inflata can be induced by a certain concentration of cadmium,and its degree is direct ratio to the dose of exogenous cadmium.The intracellular ROS and RNS levels increased at 24 h under cadmium stress,and MDA began to rise rapidly at 48 h.Cadmium inhibited the activities of SOD,GSH-PX,ACP and AKP to a certain extent,and the inhibitory effect was direct ratio to the dose of cadmium.Cadmium can induce the activity of CAT and GR,and this induction becomes stronger with the increase of cadmium dose.The response speed of MT to cadmium is proportional to the cadmium dose.The correlation analysis showed that SOD,CAT,GSH-PX,ACP,AKP,MT had negative correlation with ROS,RNS and MDA.Cadmium stress led to the overall down-regulated expression of SOD and Cd-MT,and the overall up-regulated expression of ACP,GST-MTT1 and GST-MTT2.The expression regularity of GST-MTT1 and GST-MTT1 was consistent,but the expression trend of both genes was opposite to that of Cd-MT.4.Colpoda inflata are used as indicators to monitor and evaluate the toxicity of cadmium in the environment.Under cadmium was exposed for 24 h,the biomarkers that changed significantly in the process from NOEC to LC₅₀ were MDA,CAT,ACP and GR,respectively.Under 48h,GR was the most significant change biomarker in the process from NOEC to EC₅₀,and ROS was the most significant change at LC₅₀ concentration.Under 72h and 96 h,ROS,CAT,GR,and MT were the most significant biomarkers that changed from NOEC to LC₅₀ concentrations,respectively.The environmental toxicity of cadmium can be rapidly evaluated by MDA,CAT,ACP and GR under exposure of 24 hours.