| Sulfometuron-methyl is a member of the sulfonylurea herbicides, and has been applied in the woodlands. Sulfometuron-methyl has been widely used in the world because of its low-dosage and good effect. Sulfometuron-methyl has a long period of validity, was sensitive to crops, has a strong transferability, and can contaminate groundwater. Especially, high concentration of Sulfometuron-methyl exists in industry wastewater from the manufactory of producing this kind of herbicide. Therefore, studying on the degradation of Sulfometuron-methyl is very significant. In order to screen and obtain the microorganisms degrading Sulfometuron-methyl, nineteen strains of microorganisms degrading Sulfometuron-methyl were obtained and two strains of them were found to have the highest degradation rate and of which were studied the degrading characteristics and pathways. The main results were summarized as follows:1. The microorganisms degrading Sulfometuron-methyl were screened. The nineteen strains of microorganisms degrading Sulfometuron-methyl were obtained. All the microorganisms were cultured in medium that containing different concentrations of Sulfometuron-methyl, then put in swing bed at 30℃and shook at 150 r·min-1 for 5 days, detected the concentration of Sulfometuron-methyl by using HPLC and calculated the degradation efficiency. It was shown that the degradation rates of the seven strains of microorganisms were higher in low concentration than in high concentration for Sulfometuron-methyl, with JH3 having the highest degradation rate of 98.9%, secondly, JH2 having the degradation rate of 95.3%. It was also identified that JH3 was Comamonas testosteroni, JH2 was Delftia subsp, JH10 was Bacillus subtilis, JH6 was Bacillus amyloliquefaciens, SH3 was Bacillus subtilis, SH5 was Bacillus subtilis and SH4 was salmonella sp.2. The study on the degrading characteristics and pathways of Sulfometuron-methyl degrading JH2 and JH3 strain. The results showed that (1) the optimal culture medium was the basic mediumⅢ, (2) among the Sulfometuron-methyl concentrations tested, the highest degradation rates of JH2 and JH3 strain were found in treatments with 5 mg·L-1, (3) the appropriate temperatures for Sulfometuron-methyl degradation by JH2 was 30 oC, the appropriate inoculating quantity was 1×108 CFU·mL-1, the appropriate rotation rates was 150 r·min-1 and the appropriate cultured time was 120 hours, (4) the appropriate temperatures for Sulfometuron-methyl degradation by JH3 was 35oC, the appropriate inoculating quantity was 1×107 CFU·mL-1, the appropriate rotation rates was 150 r·min-1 and the appropriate cultured time was 72 hours, (4) with mass Sulfometuron-methyl spectrometric analysis on the degradation products of JH2 and JH3 strain, it was proved that the degradation products of JH2 and JH3 strain was same. Only one degradation product spectrometric peak was obtained. The main ion was m/z198 and retention time of the spectrometric peak was 3.0 min.3. Study on extracellular enzyme activity of JH2 and JH3 strain. The key enzyme(s) involved in the initial biodegradation of Sulfometuron-methyl was localized to extracellular proteins and shown to be induced expressed. JH2'enzyme specific activity was up to 86.9 U·mg-1 at pH 8.0 and 30℃, incubation at 150 r·min-1 for 120 h,inoculum 2.3×108 CFU·mL-1 in Luria-Bertani liquid medium with Sulfometuron-methyl of 5 mg·L-1. The maximum degradation rate of extracellular crude enzymes on Sulfometuron-methyl was 86.9% at pH 8.0, 30℃in the enzymatic reaction system with Sulfometuron-methyl of 5 mg·L-1. JH3'enzyme specific activity was up to 88.4 U·mg-1 at pH 9.0 and 35℃, incubation at150 r·min-1 for 72 h,inoculum 2.3×107 CFU·mL-1 in Luria-Bertani liquid medium with Sulfometuron-methyl of 5 mg·L-1. The maximum degradation rate of extracellular crude enzymes on Sulfometuron-methyl was 91.3% at pH 9.0, 35℃in the enzymatic reaction system with Sulfometuron-methyl of 5 mg·L-1. The degrading enzyme(s) was not sensitive to high temperature and kept high activity under alkaline conditions.4. The activity enzyme of JH2 and JH3 strain degrading Sulfometuron-methyl were purified. In this study,the extracellular crude proteins of JH2 were eluted by DEAE SepHarose Fast Flow anion exchange column and five peaks were found. The proteins were detected by by a clear zone, three peaks had activity. The extracellular crude proteins of JH3 were eluted by DEAE SepHarose Fast Flow anion exchange column and two peaks were found. The proteins were detected by a clear zone, only one peak had activity. Four components (P1-1, P1-3, P1-5, P2-2) had obviously activity. The molecular weight of four components were 43 kDa, 32 kDa, 15 kDa and 46 kDa through SDS-PAGE respectively. The amino acid sequences of Sulfometuron-methyl degrading enzymes (P1-1, P1-3, P1-5, P2-2) derived from JH2 and JH3 strain were determined by MALDI-TOF-MS and four degrading enzyme were signal transduction histidine kinase, prephenate dehydrogenase, unnamed protein, and glycosyltransferase, respectively. According to the gene sequence encoding amino acids (G1-1, G1-3, G1-5, G2-2) the degenerate primers were designed. The Sulfometuron-methyl degrading enzyme genes from the genome of JH2 and JH3 were amplified by PCR and full-length gene were 1191 bp, 886 bp, 415 bp and 1274 bp, respectively. G1-1, G1-3, G1-5 and G2-2 were connected with PMD19-Vector and transfered to E. coli DH5α. Positive clones were screened out by ampicillin and determined the sequences. The obtained results were compared with gene sequence reported in the Genbank and kept accordance with gene sequence encoding amino acids (G1-1, G1-3, G1-5, G2-2) by Blast analysis.5. Preliminarily studied on bacterial agent of JH2 and JH3. The formulation of AS and GR of JH2, JH3 were obtained. The plants sensitive with Sulfometuron-methyl were screened by activity determination. The result showed that wheat is sensitive with Sulfometuron-methyl and IC50 was 0.014 mg·kg-1. The residual amount of the soil contained Sulfometuron-methyl of 5 mg·kg-1 and 1 mg·kg-1 that degraded respectively by JH2 and JH3 AS for 15 days and 20 days were lower than 0.0077 mg·kg-1.
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