The Synergistic Effect And Mechanism Of Atrazine Degradation Enhanced By Exogenous Zn²⁺ In Arthrobacter Sp. DNS10

Atrazine is widely used worldwide as a high-efficiency,low-cost herbicide.However,while atrazine achieves weed control,it also has a serious impact on the ecological environment and biological health due to its biotoxic and long-lasting properties.Microbial degradation is currently recognized as a highly efficient and green atrazine reduction technology,and how to further improve the microbial degradation effect of atrazine is worthy of deep attention.In this study,a strain of Atrazine high-efficiency degrading bacteria Arthrobacter sp.DNS10 obtained in the previous test was selected as the test strain,focusing on investigating the effect and related mechanism of exogenous Zn²⁺enhanced strain DNS10 to degrade atrazine.The main results are as follows:?1?The effect of exogenous Zn²⁺on the ability of strain DNS10 to degrade atrazine and gene expression was studied.Compared with the treatment without the addition of exogenous Zn²⁺,the addition of 0.05 m M and 1.0 m M exogenous Zn²⁺can promote the growth of the strain DNS10,of which 0.05 m M Zn²⁺has a more obvious growth promotion effect on the strain DNS10 than 1.0m M Zn²⁺,also with the increase of culture time from 32h to 56 h,the removal rate of atrazine by0.05 m M and 1.0 m M exogenous Zn²⁺cultured strain DNS10 was significantly higher than that without exogenous Zn²⁺addition treatment.At 48h incubation,the removal rate of atrazine by strain DNS10 with the addition of 0.05 m M Zn²⁺was 94.42±2.03%,and the removal rate of atrazine with 1.0 m M Zn²⁺was 86.02±1.49%.Treatment,the removal rate of atrazine is only66.43±3.59%.The study found that the addition of exogenous Zn²⁺can increase the expression of the atrazine chlorohydrolysis gene?trz N?of the DNS10 strain,in which the expression of the strain DNS10 trz N during the addition of 0.05 m M and 1.0 m M exogenous Zn²⁺in the 48h of the entire cultivation stage The amounts were 1.91±0.03 and 1.11±0.05 times of the gene expression of the strain without Zn²⁺treatment.?2?The effect of exogenous Zn²⁺on the cell membrane characteristics and transmembrane transport of the strain was studied.Studies have shown that compared with the treatment without the addition of exogenous Zn²⁺,the surface of the DNS10 bacterial cells treated with 0.05 m M Zn²⁺exhibits protrusions,and the roughness of the bacterial cell surface also increases.Adsorption sites and areas of contact.The zeta potential of the strain DNS10 without Zn²⁺treatment was-10.83±0.70 mv,and the zeta potential of the strain DNS10 with 0.05 m M Zn²⁺addition treatment was-13.23±0.76 mv,indicating that the exogenous Zn²⁺treatment can make the strain DNS10exhibit stronger electronegativity.In addition,the results of flow cytometry analysis showed that:0.05 m M Zn²⁺significantly increased the membrane permeability of strain DNS10.by measuring the accumulation of atrazine in cells,it was found that the addition of low concentration Zn²⁺?0.05m M?The concentration of atrazine accumulated in cells of DNS10 strain was 0.0093 mg·g^-1?48 h?,which was 2.21 times higher than that without Zn²⁺treatment.However,the high concentration?1.0 m M?of Zn²⁺had a relatively small regulation effect on the DNS10 membrane permeability and atrazine accumulation.The addition of exogenous Zn²⁺can also increase the DNS10 ATPase activity of the strain.Among them,the ATPase activity of the strain was the highest at 32 h.The ATPase activity of the strain treated with 0.05 m M Zn²⁺was 11.34 times higher than that without Zn²⁺.?3?Extracellular polymer?EPS?exists as a macromolecular organic substance on the surface of degrading bacteria.Its complex components and groups play an important role in the surface adsorption of atrazine.Therefore,the composition of EPS produced by strain DNS10 in the absence of Zn²⁺and 0.05 m M exogenous Zn²⁺and the effects and related mechanisms of combining atrazine characteristics were studied.The results showed that the extracellular polymer produced by strain DNS10 was mainly composed of polysaccharides,proteins and a small amoun t of humic acid,and their contents were 598.84±3.95,90.87±5.24 and 12.42±1.90 mg·g^-1,respectively,and added with 0.05 m M Zn²⁺The main components of EPS changed,mainly promoting the content of protein and humic acid in EPS,which were 139.20±3.91 and 48.46±2.62mg·g^-1,respectively.Three-dimensional fluorescence spectrum scanning revealed that the fluorescence intensity of humic acid in EPS produced by strain DNS10 was significantly enhanced in the presence of 0.05 m M exogenous Zn²⁺.After the EPS is combined with atrazine,the fluorescence intensity of the protein-like substances contained therein is obviously quenched,and the humic acid is completely quenched,indicating that the protein and humic acid in EPS are in the process of combining with atrazine Plays an important role.After the two EPS are combined with atrazine,the functional groups such as hydroxyl,carboxyl and carbonyl of protein and polysaccharide in EPS and benzene ring in humic acid are shifted to different degrees,indicating that the protein,polysaccharide and humic acid in EPS Inseparable in the process of adsorbing atrazine.