Screening Of Atrazine-degrading Bacterias And Metabolic Pathway Of Atrazine In The Oligotrophic Conditions

In recent decades, Representative S-triazine herbicide atrazine is widely usedaround the world for its good performance on weeding and low prices, Currently, Theresearches related to the removal of pesticide in soil and pesticide factory are more thenthe studies about biological degradation of pesticides in source water. Microorganismsare capable of using carbon, nitrogen, phosphorus and other nutrients in natural water,They can also use pesticides as nutrients for growth, Face to the challenges of waterpollution caused by pesticide residual, microbial degradation of pesticide residuesbecome a viable means to address this major problem.In this topic, the mixed sludge from the sewage treatment plant was domesticatedby SBR method and artificial water (micro-polluted raw water). Then anatrazine-degrading strain has been isolated and purified successfully. The strain has thecharacteristics of faster degradation of atrazine, high degradation rate and geneticstability. It was identified (named bacteria3). The growth and degradationcharacteristics of strain3andstrain1(Pseudomonas bacteria was domesticated throughhigh concentrations of atrazine in the previous research) were studied by OD600andatrazine degradation rate Respectively, Atrazine degradation pathway was studieddeeply, all that can provide a theoretical basis and technical support for removing traceamounts of atrazine in drinking water and micro-polluted water bioremediation byengineering methods.A higher atrazine degradation strain has been isolated and purified successfully.According to physiological and biochemical characteristics and16S rRNA geneidentification, the strain was judged as Stenotrophomonas maltophilia bacteria(Stenotrophomonas maltophilia sp.) Bacteria (Genbank Accession No. KF551915).The optimal pH for the growth of strain1and strain3is6~9and7~8, respectively.Both two strains grown well at20℃~30℃. They are aerobic bacteria and the optimal is150r/min for both. Strain1and strain3are able to use atrazine as the sole nitrogensource, but can not use atrazine as carbon source. The both strains can use glucose,fructose, sucrose, and sodium citrate as the carbon source, Strain1can use starch ascarbon source, but that can not be used by Strain3. The available nitrogen sources forthe both strains include yeast extract, peptone, ammonium nitrate, ammonium chlorideand potassium chloride.A good degradation of strain1and strain3has been observed in the conditions ofhigh concentration (100mg/L) and low concentration (0.2mg/L) of atrazine. Atrazinedegradation by strain1is inhibited by Cu2+, however it has no effect on strain3. The other heavy metal ions (As5+, Cr3+, Cd2+and Pb2+) do not have a great impact on thedegradation of atrazine by strain1or strain3. Atrazine degradation by strain1combined with strain3is similar with which by strain3separately. Both strain1andstrain3degrade simazine effectively, and the degradation rate can reach above85%.Strain1and strain3are both the heterotrophic nitrification bacteria. There are threeintermediate degradation products, de-ethyl-atrazine, de-isopropyl-atrazine andde-chloro-atrazine. The produce of them is non-sequential. Finally they are mineralizedto ammonia, carbon dioxide and water. Ammonia is converted to nitrate by nitrification.The nitrification occurs mainly after cells stop growing.