The Effect Of Carbon Source To Promote The Remediation Of Bensulfuron-methyl Contaminated Soil By Hansschlegelia Zhihuaiae S113

Bensulfuron-methyl（BSM）,a representative variety of sulfonylurea herbicides,is widely used in the removal of weeds in the field because of its high herbicidal activity,good crop selectivity,and low toxicity to mammals.In recent years,the usage and area of sulfonylurea herbicides have continued to increase,causing serious residues in farmland soils,which caused phytotoxicity to the rotation-sensitive crops.Therefore,the remediation of bensulfuron-methyl contaminated soil has become an urgent problem to be solved.Using microorganisms to degrade herbicide residues in the soil is a safe,efficient,and non-secondary pollution method.In this paper,the high-efficiency BSM-degrading strain Hansschlegelia zhihuaiae S113 stored in the laboratory was used to study the effect of adding carbon sources to promote bioremediation bensulfuron-methyl contaminated soil by S113.By setting up treatments with different substances including glucose,sodium succinate,and sucrose,the effect of carbon sources on the promotion of the degradation of BSM residues in the soil by strain S113 and the degradation pathways were studied;the dynamics of bacterial community structure and abundance in different treatments were analyzed;BSM intermediate metabolite 2-（aminosulfonylmethyl）-methyl benzoate（MSMB）degrading strain was isolated,and its degradation characteristics and metabolic pathways for MSMB were studied.The results of this study provide some new basis for the study on the mechanism of remediation of BSM contaminated soil by adding a carbon source cooperated with strain S113.The main contents and results of this study are as follows:1.Adding carbon source promoted the remediation of bensulfuron-methyl contaminated soil by strain S113Glucose,sodium succinate,and sucrose were added to the BSM contaminated soil combined with strain S113 repairing,and the residual amount of BSM and the production of benzylsulfonic acid were detected.The results showed that all of the three-carbon sources could promote the degradation of BSM by strain S113 in the soil.Among them,glucose had the best promotion effect on the degradation rate of BSM,which reached 98.7%on the ninth day.The metabolites of BSM in different treatment soils were identified by HPLC-MS/MS.Except for benzsulfonic acid,which is the product of bensulfuron-methyl degraded by S113,six main products were detected in the treatment and they were identified as 2-[（carboxymethylamino）sulfonylmethyl],2-amino-4,6-dimethoxypyrimidine（ADMP）,methyl2-（sulfamoylmethyl）benzoate（MSMB）,2-（sulfamoylmethyl）benzoate,（4,6-dimethoxypyrimidin-2-yl）urea and lactohydroxymethyl benzoate,respectively.Based on these degradation products,the metabolic pathway of BSM was inferred,including cleavage of the phenyl ring ester bond,pyrimidine ringside urea bridge peptide bond cleavage,benzene ringside urea bridge peptide bond cleavage,C-S bond cleavage and cyclization.Through hydroponic experiments and microbial growth inhibition experiments,the effects of BSM,MSMB,and ADMP on the growth of plants and microorganisms were studied.The results showed that BSM,MSMB,and ADMP could inhibit the growth of corn,sorghum,and three microorganisms to a certain extent,and their inhibitory effects are from large to small:BSM>ADMP>MSMB.2.The microecological effect of carbon source promoted the remediation of bensulfuron-methyl contaminated soil by strain S113High-throughput sequencing was used to further explore the dynamic change process of bacterial community structure in soil samples on the 5th,10th,15th,and 20th days of different treatments.Alpha diversity analysis showed that different carbon sources,strain S113 and BSM all contributed to increasing the diversity and richness of soil bacterial communities.Beta diversity analysis showed that the five treatments,the addition of BSM,strain S113,strain S113+BSM,glucose+strain S113+BSM,sodium succinate+strain S113+BSM,and sucrose+strain S113+BSM,are quite different from CK,which probably due to the addition of carbon source and strain S113.The relative abundance of species at the phylum level showed that sodium succinate,sucrose,strain S113 and BSM have an inhibitory effect on the relative abundance of Actinobacteria,while the treatment of glucose+S113+BSM could promote it.The relative abundance results at the genus level indicated that Hansschlegelia could not use the intermediate metabolites of BSM for growth.BSM inhibited the growth of bacteria belonging to the genera Arthrobacter and Sphingomonas.The relative abundance of Noviherbaspirillum in the later period and Rhodococcus is increasing.It is possible that the strains in these two genera are involved in the degradation of the intermediate metabolite of BSM,and could grow with the intermediate metabolite of BSM as a carbon source.In the treatment with the addition of glucose+S113+BSM,the number and proportion of the genera with relatively large abundance were higher than other treatments,indicating that the strains in these dominant genera had a preference for glucose as a carbon source.3.Identification,degradation characteristics and metabolic pathway of methyl 2-（sulfamoylmethyl）benzoate degrading strain SJT-4A strain SJT-4,capable of degrading methyl 2-（sulfamoylmethyl）benzoate（MSMB）,was isolated from the soil treated with glucose+S113+BSM.The strain was identified as Rhodococcus sp.by the analysis of physiological and biochemical characteristics and 16S r RNA gene sequence.Strain SJT-4 could degrade about 97.6%of 50 mg/L MSMB within 45h.The optimum temperature and p H for the degradation of MSMB by SJT-4 were 40°C and8.0,respectively.Fe³⁺、Al³⁺、Ca²⁺、Zn²⁺、Li⁺、Ni²⁺and Co²⁺could promote the degradation of MSMB by strain SJT-4 and Fe³⁺had the most significant promoting effect while Cu²⁺had a significant inhibiting effect on degradation.The metabolites were analyzed by HPLC-MS/MS,and the metabolic pathway was presumed to be that strain SJT-4 could directly cyclize MSMB into finally generated 1H-2,3-benzothiazin-4（3H）-one 2,2-dioxide.In addition to MSMB,SJT-4 also had the effect of degrading the diphenyl ether herbicide lactofen and the fungicide trifloxystrobin.