| Atrazine(6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine)are among the most used members of triazine herbicide,are toxic,can be persistent and widely distributed in the environment.The environmental contamination of these compounds is considerable,may pose a significant threat to,agricultural production and the environment.In this study soils from sugarbeet-cultivated fields were screened for bacterial species capable of atrazine degradation through enrichment culture method.Furthmore,degrading bacteria was identified.Its degradation effects were analyzed.Two bacterial strains Y1 and Y2 isolated from sugarbeet fields had shown a degradation of 31.63 and 30.12%of applied amount in100 mg/L atrazine liquid culture at72h.On the basis of morphological appearance,physiological nature and 16SrDNA analysis,Y1 show highly sequence similarity to Klebsiella peneumoniae.Another bacterial sp.,Y2 was closely related to Bacillus pumilus.Y1 and Y2 can grow fast in the pH value of 4-9.The optimal pH for Yl and Y2 are 7.0 and 6.0 respcetively.The Yl and Y2 grew best when the temperature is 30 ?and 36?.In addition,the optimum carbon and nitrogen source for Y1 is maltose and yeast extract respectively.The optimum carbon and nitrogen source for Y2 is sucrose and beef peptone.Bioassay result showed that the seeding emergence of suger beet was not affected by the atrazine,but it affected the growth of suger beet seriously.High concentrations of atrazine can cause sugar beet seedling death;Low concentrations of atrazine did not lead to the sugar beet seedling death,but reduced the dry weight of sugar beet seedling seriously.Soil contained chlorimuron-ethyl can keep seedlings dry biomass,chlorophyll contents and photosynthesis rate by appliying degarding bacteria.The recover roles of Y1 and Y2 were most prominent when the atrazine was 90?g/kg.which the total dry biomass of sugarbeet seedlings enhanced 249.82%and 413.46%compared to that in applied atrazine control. |
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