| Cadmium(Cd)is a heavy metal that causes water pollution.After entering the animal or human body through the food chain,it can cause important health risks and even induce a variety of diseases.As a common cladoceran,Daphnia magna has the characteristics of transparent body,strong fecundity,sensitive to chemicals in water,simple structure and so on.It has become one of the model organisms for aquatic animal toxicology.In order to study the effects of cadmium exposure on the gut microbiota and lipid metabolism of Daphnia magna,three-day-old Daphnia magna were treated with 0,0.01 and 0.09 mg/L cadmium solution for 24 h and 48 h,respectively.Metagenomic microbial classification sequencing was used to analyze the changes in the number,species and structure of gut microbiota in Daphnia magna.At the same time,gas chromatography-mass spectrometry(LC-MS)was used to quantitatively analyze seven short-chain fatty acids in Daphnia magna.Finally,three-day-old Daphnia magna were treated with 0,0.01,0.05 and 0.09 mg/L cadmium solution for 1 h,12 h,24 h and 48 h,respectively,and the changes of lipid metabolism related indicators were detected.The experimental results are as follows:1.The dominant bacteria of gut microbiota in Daphnia magna are Bacteroidetes and Proteobacteria.Cadmium stress can lead to increased gut microbiota diversity of Daphnia magna.Compared with the control group,the relative abundance of Proteobacteria decreased significantly and Verrucomicrobia increased significantly(P<0.01)when cadmium stress was 24 h and the concentration was 0.01 mg/L.At high concentration of0.09 mg/L,the abundance of Bacteroidetes decreased significantly(P<0.01),the abundance of Proteobacteria and Firmicutes increased significantly(P<0.05,P<0.01),and the abundance of Probiotics increased significantly(P<0.01).2.Seven short-chain fatty acids(acetic acid,propionic acid,isobutyric acid,isovaleric acid,valeric acid,butyric acid and hexanoic acid)in Daphnia magna were quantitatively analyzed by gas chromatography-mass spectrometry(LC-MS).The contents of acetic acid,propionic acid,butyric acid and valeric acid decreased,but the content of isovaleric acid increased when the concentration of cadmium solution was 0.01 mg/L and0.09 mg/L for 24 h.The content of propionic acid,isobutyric acid,butyric acid,valeric acid and hexanoic acid increased and the content of acetic acid decreased when the concentration of cadmium solution was 0.01 mg/L for 48 h.When the concentration was0.09 mg/L,the content of butyric acid,valeric acid and caproic acid increased,and the content of acetic acid,propionic acid,isobutyric acid and isovaleric acid decreased.3.After treatment with 0,0.01,0.05 and 0.09 mg/L cadmium solution for 1 h,12 h,24 h and 48 h,the TG content and FAS activity of Daphnia magna increased at 0.01 and 0.05mg/L,and decreased at 0.09 mg/L within 1～24 h.After 48 h of treatment,the activities of TG content and FAS activity decreased.Compared with the control group,the activity of ACC increased at 0.01 and 0.05 mg/L,and decreased at 0.09 mg/L after cadmium treatment for different time.LPS activity increased at 0.01 and 0.05 mg/L cadmium treatment for 1 and 12 h;At a concentration of 0.09 mg/L,it decreased;At 24 h and 48 h of cadmium treatment,it decreased at 0.01 and 0.09 mg/L,and increased at 0.05 mg/L.The activity of LPL increased at 0.01 and 0.05 mg/L of cadmium treatment for 1 h,and decreased at 0.09 mg/L;at 12 h of cadmium treatment,the concentration of 0.01 and 0.09mg/L decreased,and the concentration of 0.05 mg/L increased;After 24 h of cadmium treatment,it increased when the concentration was 0.01 mg/L,and decreased when the concentration was 0.05 and 0.09 mg/L;cadmium treatment for 48 h,the concentration of0.01,0.05 and 0.09 mg/L decreased. |
