Separation Of The Herbicide Atrazine Degradation Strains Identification And Its Degradation Characteristics Research

Atrazine is a kind of triazine herbicide widely used in farmland. High residue will cause chemical hazards to some sensitive aftercrops by long-term using, for it is rather stable in nature. So researchers focus on the bioremediation of the atrazine-polluted soil. This study includes five aspects which are isolation, identification of the atrazine-degrading strains, groping of effect factors, primary study of degradation mechanism, preparation and application of the solid microbial inoculum, and the results are as follows:In this study, the strain T3AB1 capable of utilizing atrazine as sole nitrogen and carbon source was isolated from maize field suffering atrazine in Nehe, Heilongjiang.It was detected by HPLC that the strain could degrade more than 99% of 500mg/L atrazine within 72h. The sensitive aftercrop statistical trials showed that, the strain would come into effect in application.Subsequently, morphological characteristics of the strain was known from Optical Microscope, Scanning Electron Microscope and Electron Transmitted Microscope. Physiological biochemical characteristics were clear from the reactions including 27 terms,48 indexes. 99% similarities with the strains belonging to the genus Arthrobacter was known by 16S rDNA gene sequence determination and blast. The gene sequence was submitted to Genbank and the accession number GU459313 was recorded. According to morphological, physiological biochemical characteristics and the homology analysis of 16S rDNA gene sequence, it was initially identified as Arthrobacter sp.The degradation of atrazine was influenced by external condition around the strain. In this study, we tried to find out the influence which was caused by incubation time, temperature, pH, extra carbon and nitrogen source, atrazine primary concentration and inoculation amount on the strain growth and atrazine degradation.The better degradation condition was as follows:100 to 500mg/L atrazine of inorganic salt medium, pH7.0 to 8.0,0.5-2.0% inoculation amount,25-30℃, 200r/min shaking 72-108h, the degradation can reach above 99%; extra carbon glucose (100-500mg/L) and extra nitrogen ammonia sulfate (100-900mg/L) could accelerate the degradation to some extent, and the OD600 was higher than the treated without any extra carbon or nitrogen source.Primary study of degradation mechanism showed that, the degradation of the strain to atrazine was mainly due to the enzyme in vivo which was stimulated in 300-500mg/L of atrazine. The conservative fragments of the first three atrazine-degrading related genes of the strain were amplified as the combination of trzN, atzB and atzC. The accession number of the whole trzN sequence we got from Genbank is GU459313, and the sequence (1371bp) determined showed 99% similarities with those from the representative strains. The structure and function prediction of the protein coded by trzN (GU459313) was analysed by SWISS-PROT and CBS and showed a few differences from the reported triazine hydrolases.As to application of the degrading strain, our study began with the preparation of the solid microbial inoculum. Then we compared the degradation to atrazine of the inoculums with different supporters. Among them, we selected an ordinary and more efficient process, refrigeration and drying without supporters, to apply in microbial remedy for simulated polluted soil. And the sensitive aftercrop test results indicated that the inoculum was a good one to apply in microbial remediation for polluted soil.In a word, our result may be useful to the following research of the bioremediation of atrazine polluted soil.