Research On Characteristics Of A Butachlor Degrading Bacterium C-5

Butachlor is produced by Monsanto Company of America in1969on the basis of propachlor,which is applied in rice fields to control weeds. With the excellent characteristics of low dosage、high activity and selectivity, the amide herbicide butachlor had recently become a widely used herbicide with large application amount in rice production. Although butachlor is not a herbicide of long persistence, but its residual time in soil is also more than a month. Due to its deposition in plants、water and soils, the environmental contamination caused by butachlor was quite serious. The butachlor’s disappearence in soil was due to the degradation of microorganism. A bacterial strain named C-5, capable of utilizing butachlor as sole carbon source, was isolated from butachlor-contaminated soil in sewage outfalls and waste reservoirs of several pesticide factories using enrichment culture technique.The growth characteristics and degradation characteristics of C-5were studied at different environmental conditions. Bioremediation of C-5on rice seedlings was examined under laboratory conditions. The biodegradation products of butachlor were identified by GC-MS and initial degrading pathway was discussed.The results were as follows:1:Bacterial strain C-5with perfect degrading effect on butachlor was identified as Delftia sp based on its morphology,physiological and biochemical characteristics and16S rDNA homologue sequence analysis.Then C-5’s gene sequence was registered and GenBank Accession number is KC702840.2:The optimal conditions for growth of C-5were pH7.0and30℃, respectively. When initial concentration of butachlor was20mg/L and inoculation amount of C-5was5%(OD600=1.34), more than76%of butachlor was degraded by C-5without additional carbon source.3:Bioremediation of C-5on rice seedlings treated with butachlor of5mg/L and inoculation rate of10%was examined under laboratory conditions.When rice was incubated on the condition of30℃and photoperiod of16h light,8h dark for5d,emergence rate could reach87%,only10%lower than the blank control, while50%higher than the group without inoculation of C-5; Plant height was44%lower than the blank control,wihle93%higher than the group without inoculation of C-5. Analyses of emergence rate and plant height of rice seedlings indicated that bioremediation effect of C-5was over50%.4:Three metabolites produced during butachlor degradation by C-5were identified based on Gas Chromatography(GC) and Gas chromatography-mass spectrometry (GC-MS):2-chloro-2’,6’-diethylacetanilide and N-(2,6-Diethyl-pheny)-N-hydroxymethyl-formamide;(2,6-diethyl-phenyl)-ethoxymethyl-carbamic acid then the probable degradation pathway was proposed.