Study On Atrazine Degradation Community DNC5Characteristics And Soil Remediation Effect

Atrazine is the most widely used herbicide in Northeast China now. Meanwhile, as a typicalorganic pollutant, its impact on ecological and environmental issues is also increasingly serious.This paper chose an atrazine degrading bacterial consortium DNC5which was isolated inlaboratory as the research object; study the consortium DNC5atrazine degrading ability,consortium composition and consortium functions. At the same time strain DNS10which wasisolated from consortium DNC5, has been studied on the atrazine degradation ability, growthcharacteristics and degradation pathway, and the degradation genes containing strain DNS10ofgene cloning and gene location. Finally, a preliminary study was carried out on the repair effect ofatrazine degradation consortium DNC5on the polluted soil.When the inoculation amount was1%(v/v, concentration of bacteria suspension is OD₆₀₀=1)into the medium (the initial atrazine concentration was100mg·L^-1), all the atrazine was degradedafter40h’s culture. Through the direct method of isolation and liquid enrichment culture medium,we found the consortium DNC5was composed by four kinds of pure cultural strains. Combiningthe analytical results of the16SrRNA sequences, these four kinds of strains were named asBacillus subtilis DNS4、Arthrobacter sp. DNS9，Arthrobacter sp. DNS10and Variovorax sp.DNS12.The results of substrate utilizing tests further indicate that only strain DNS10could utilizeatrazine as the nutrient materials for growth among these four strains. Strain DNS4and strainDNS12could utilize the metabolites of atrazine degradation that cyanuric acid as the nitrogensources for growth. Thus, strain DNS9could use ethylamine and isopropylamine that another twokinds of atrazine degradation metabolites for growth. Additional typical nitrogen experimentsshow that the typical nitrogen source addition could promote the growth of bacteria, but does notchange the original characteristics of strains. Only strain DNS10in the consortium DNC5candegrade atrazine. Co-metabolism phenomenon has not been found in the other three pure culturestrains under the simple nitrogen condition. Furthermore, addition of isopropylamine (100mg·L^-1)inhibited atrazine degradation by strain DSN10.Artificial constructed atrazine degradation consortium experiment results showed that thedegradation rate of the combinations （except combination without DNS10） and consortium DNC5was better than that of strain DNS10alone. Not only once again that the key role of strain DNS10, also shows that there is a certain synergistic effect between strains.Primers of atzA, atzB, atzC and trzN, atzD, atzE, atzF, trzD were designed referring to formerliteratures. The total DNA of DNS10acted as the DNA model to carry on PCR （polymerase chainreaction） and atzB、atzC and trzN genes in DNS10were cloned. The results showed that strainDNS10could degrade atrazine to cyanuric acid. At the same time, using the HPLC method text theend products of strain DNS10degrading atrazine, there was some cyanuric acid accumulated in themedium (final concentration was66.13±2.11mg·L^-1) when all the added atrazine (initialconcentration was100mg·L^-1) has been degraded by strain DNS10. According to the above resultsshow that strain DNS10can be degraded atrazine to cyanuric acid completely.Through the reported matter extraction and detection methods proved that a plasmid in whichsize was more than23Kb was in strain DNS10. The total DNA of DNS10and DNS10-PE acted asthe DNA model to carry on PCR respectively，and the result indicates that The three kinds ofatrazine degrading genes were located on the plasmid. The results show that a close relationshipexisted between the degradation ability of strain DNS10and the plasmid.On the basis of these researches, atrazine degradation by consortium DNC5in soil was studied.After the repair process after25days, adding consortium DNC5repair in soil samples treated withbasically no atrazine was detected. Though the concentration of polluted treatment got smallerduring the experimental period, the final atrazine concentration was still9.98±1.31mg·kg^-1. Theadded consortium DNC5could accelerate the atrazine decomposed speed. Combined with therepair process soil samples key soil enzyme activities to flora DNC5the repair process ofatrazine-contaminated soil ecological safety of a preliminary evaluation. The results show thatatrazine degrading consortium DNC5has certaineffect on soil enzyme activity of atrazinecontaminated soil, all containing atrazine treatments showed the same trend on urease andphosphatase: first restraining then stimulating. And invertase significantly inhibited. Thedegrading bacteria DNC5contaminated soil urease, invertase activity has a role in promoting andwithout adverse effects for phosphatase activity.