Research About Toxic Effects Of Atmospheric Compound Pollutant Dust On Human Common Bacteria

In this study,the ultrafine mineral particles quartz and calcite were chosen as the carrier of composites particles,main heavy metal pollutants Pb(?)/Cd(?)and typical organic matter Benzopyrene(Bap)as extra pollutant to form compound pollutant dust.Experiments were carried out to explored the membrane damage effect and toxicity mechanism of human common bacteria,Escherichia coli(E.coli).From changes on cell membrane biomolecules and oxidative damage or membrane damage,study the interaction and interface membrane effect between the different mineral dust,heavy metal coated onto pollutant dust,compound pollutant dust and human common bacteria.In this study,E.coli was selected as the research object.Air pollution dust was prepared by an artificial method and its basic characteristics such as surface morphology,particle size,Zeta potential,and free radical production were characterized.The results show that the heavy metal and organic matter has little effect on the particle size of the dust,but,Zeta value has a greater change;after treated with Ultrasonic disperser,with the increase of amount added of Pb/Cd and organic matter,the active substances of compound pollution dust such as oxygen content also gradually increases.The main components of cell membranes such as bovine serum albumin(BSA)and phospholipid molecules were studied by means of 3D fluorescence,Infrared Spectroscopy,and Microcalorimetry.It was found that compound pollutant dust and heavy metal-loaded dust adsorbed on the surface of biological macromolecules,mainly due to the electro static attraction between each other;Infrared Spectroscopy test indicated that heavy metal and compound pollutant dust mixed with BSA protein,the results show its basic structure changes a lot due to the interaction with dust.FTIR peak resolution and fitting technique were used to calculate the peak area and analyze the secondary structure changes,it was found that the changes are mainly reflected in the decrease of ?-helices and ?-turns in the secondary structure of BSA,while the content of ?-sheets increased.During the interaction between the two research object,?-helices and ?-turns are converted into ?-sheets,and hydrogen bonds are formed between the dust and the polypeptide chains,which leads to the unwinding of the peptide chain of BSA and increases the degree of protein disorder.Compound pollution dust will cause the characteristic fluorescence peak of phospholipid molecules weaken in a short time,and the intensity will gradually decrease with the increase of the interaction time.These experiments show that those particles have an effect on the chromophoric groups such as aromatic rings in the phosphatidylcholine molecule,which causes fluorescence quenching.In the process of damage,the generation of free radicals in the liquid phase environment of the dust will change the structure of the BSA and phospholipids.Finally,as a result,the cell membrane loses its normal function.It will affects normal cellular physiological activities.The toxicity of Pb(?),Cd(?)and complex contaminants both can lead to the toxicity of E.coli.The main manifestations are oxidative damage and cell membrane damage.After E.coli was treated with single heavy metal ions and complex pollutant dust respectively,the cell survival rate decreased,and with the increase of heavy metal concentration.the survival rate gradually decreased.While the organic matters at different concentrations had no significant effect on the cell survival rate,which may be due to Concentration is too low or volatilization during preparation.Compared with the control group,the production of ROS and MDA in the E.coli increased and the amount of PI in the cells increased after the interaction with two heavy metal ions,complex heavy metals and organic dust,and the pictures of Confocal micro scope also confirmed that the E.coli cell membrane was damaged at a certain degree.In the infrared characterization,the effect of dust on the surface groups of the cell membrane was mainly concentrated on the characteristic absorption peak positions of the phosphodiester groups and proteins.After FTIR peak resolution and fitting technique.The results showed the ratio of ?-sheets/?-helices in the amide I band of the secondary structure of the protein was significant decreased.It indicated that the conformation of the protein has changed.In the liquid phase,the results show that the mineral dust will generate a certain amount of reactive oxygen species,and the cell membrane changes due to the oxidative damage produced by free radicals,which is an important toxic mechanism.For the combined toxic effects of compound pollution dust,there were significant interactions between particulates mixed with Pb(?),Cd(?),and Benzopyrene,in the low concentration of heavy metal coated onto dust group,The combined toxicity effect on E.coli was slower than single heavy metal ions;the toxic effects on E.coli were shown to be synergistic in the high-concentration heavy metal dust group.The characteristics,composite forms,and heavy metal species and content of particulate matter were all different,which will show different toxic effects.Studies have shown that interaction between micro-organisms and composite dust,the particulate matter and its active substances first act on the wall structure of bacteria and interact strongly with some components of the cell membrane,destroying its normal structure and function.Affects the integrity and permeability of the cell membrane,and the normal physiological activity of the cell is disturbed,leading to inactivation and even death.