Isolation, Identification And Characterization Of Atrazine-Degrading Bacterias In Oligotrophic Conditions

As a widely used herbicide, Atrazine has caused serious environmental pollution of soil, surface water and groundwater, due to its special physical and chemical properties. Atrazine and its metabolites to most of the time provides a potential human health risk,and therefore to explore a simple and reliable removal is particularly important. At present, the rearch of analysis, presence, fate and removalon on pesticides and other endocrine disrupters are most focus on contaminated soil and pesticide plant sewage both at home and abroad.Most research still concentrate on the atrazine degeneration fungus separation in the soil, the biodegradation mechanism research and the soil biology repair technology,while the few studies on biological removal of such substances in the source water and drinking water.There are rarely reported in isolation of atrazine-degrading strains in the oligotrophic conditions through aeration acclimation.Therefore it is of great dignificance to isolate atrazine-degrading bacterias and carry out the removal of trace atraine in micro-polluted water source condition.The sludge mixture from the sewage treatment plant were cultured by aeration method with poor nutrition raw water and domesticated steadily by the way of SBR(Sequencing Batch Reactor) in reactor with hanging padding.The experiment water was poor nutrition raw water of manual configuration with trace atrazine as nitrogen source.Aerated2h running, standing lh, go on after Qing dynasty to rejoin the original running water aeration.Run the reactor at a temperature around25℃, DO in4-5mg/L,pH value maintain, COD value of about10.2mg/L, ammonia nitrogen, a value of approximately3.9mg/L.To make sure the system stability and activity of activated sludge.entering the water leakage CODMn, NH3-N, UV254, the turbidity, the sludge shape and so on in the run-time.Two atrazine-degrading bacterias named L-1and L-6were isolated from the sludge mixture an.These bacterias could grow with atrazine as unique nitrogen source and produce significant degradation bands on atrazine solid medium.Through the scanning electron microscope, the L-1cells showed the variation characteristics of the ball and bar obviously:the young cells showed short rod and the aging cells showed spherical, and the L-6cells showed long rod regularly. Based on16S rRNA gene sequences and combing with physiological and biochemical testing, L-1was identified as Arthrobacter sp.(Genbank Accession No. FJ378034) and L-6was identified as Pseudomonas sp.(Genbank Accession No. HQ285878).The growth characteristics of two atrazine-degrading bacterias were investigated in order to provide a scientific basis for the bactria of high concentration and batch fermentation.The optimum growth temperature of L-1was20-30℃and the initial pH was7.0-8.0.Carbon use indicated that L-1-degrading bacteria could utilize glucose, fructose and other common carbohydrate for its growth,while could not use starch.The optimum growth temperature of L-6was25-35℃and the initial pH was7.0-9.0.Carbon use indicated that L-6-degrading bacteria could utilize glucose, fructose and citric acid sodium as carbon sources, while could not use sucrose, lactose and starch. The two atrzaine-degrading strains could use common nitrogen sources,and the use of organic nitrogen sources such as east extract and peptone was better than the ammonium nitrate and other inorganic nitrogen.Two atrazine-degrading strain had a wide range of carbon and nitrogen and can grow well at carbon-nitrogen ratio between2/1-8/1.In minimal medium, these two atrazin-degrading bacterias were able to degrate atrazine of0.2mg/L up to94.8%and90.2%respectively within96hours.Incubation temperature and pH conditions had a great impact on the degradation of the degrading bacteria, and both had synergistic effects.The optimum degradation temperature of L-1is25-30℃and the initial pH was7.0-8.0.And the optimum degradation temperature of L-6is25-30℃and the initial pH was7.0-8.0.Carbon use indicated that some glucose and fructose as carbon souces could promote the degradation.Little effect were on the degradation efficiency of the two degrading bacterias in the case of competitive nitrogen exists.Two atrazine-degrading bacterias could be a very good adaptation to the pollution of water sources in the environment and would not seriously affect the efficiency degradation of low-concentration range.A preliminary study on the degradation pathways of the two atrazine-degrading bacterias.Results showed that two degradation bacteria could be catalyzed atrazine dechlorination.Degradation by two bacterias under the catalysis of atrazine dechlorination degradation of dynamic study, the chloride ions accumulated obviously.