| The chemical properties of carbendazim are relatively stable.It is a long-acting broad-spectrum and low-toxicity benzimidazole fungicide.It can be widely used in the control of fungal diseases of field crops,vegetables,fruit trees and other commercial crops.Due to the development of drug resistance,it is used frequently and in high doses during the growth and storage of agricultural products,resulting in varying degrees of residual contamination in common food and drinking water.In addition,the potential toxicity of carbendazim can directly or indirectly interfere with the normal physiological metabolism,endocrine system,immune system and reproductive function in living organisms,which poses a serious threat to the health of humans and animals.Therefore,it is necessary to use an efficient,economical and environmentally friendly method to efficiently degrade carbendazim.In this study,a new strain that can efficiently degrade carbendazim was screened and purified,the16 S r RNA gene sequence was analyzed,and the metabolites formed by its action of carbendazim were determined;the key degrading enzymes were isolated and purified by affinity chromatography,and their degradation mechanism was discussed in combination with bioinformatics software;the gene regulation pathway was studied by transcriptome sequencing technology,and the degradation mechanism of carbendazim by degrading bacteria was analyzed.The results of this research are concentrated in the aspect of pesticide bioremediation,which provides a more important theoretical basis and has considerable application potential.The main findings of the paper are as follows:1.In the soil of vegetable production base using carbendazim,five gram-negative bacteria strains that can grow normally with carbendazim as the sole carbon source were isolated and screened.The degradation rate of carbendazim with an initial concentration of 50 mg/L reached more than 88% within 4 days.Based on comprehensive morphological characteristics and 16 S r RNA sequence analysis,the five strains were preliminarily identified as Chitinophaga sp.DJL-A,Pantoea sp.DJL-B,Pseudomonas sp.DJL-C,Acinetobacter sp.DJL-D and Acinetobacter sp.DJL-E.Among them,Pantoea sp.DJL-B was the first discovered carbendazim-degrading bacteria species,showing the most significant degradation ability,with a degradation rate close to 95.3%.Through HPLC-MS detection and analysis,the bacteria can gradually degrade carbendazim into a series of intermediate products such as 2-aminobenzimidazole and 2,6,7-trihydroxybenzimidazole,and finally decompose them completely.2.The protein solution with degradation effect was isolated and purified from the crude enzyme solution of strain DJL-B by affinity chromatography.The highest degradation rate of carbendazim was 44.7% detected by HPLC within 4 hours.Combined with the identification of protein profiles,bioinformatics methods and review of relevant literature,it can be inferred that Arylesterase may be the key degrading enzyme,which is an α/β hydrolase with a total of 273 amino acids and a theoretical molecular weight of 29.87 KDa,and contains conserved catalytic triplet.3.The biodegradation mechanism of carbendazim by strain DJL-B was discussed from the transcriptome level.A total of 1135 genes were observed to be differentially expressed under the effect of carbendazim,including 440 up-regulated genes and 695down-regulated genes.It covers genes related to carbendazim degradation,as well as a series of genes related to environmental change perception,stress response,material transport,and carbon and nitrogen energy metabolism,such as transcriptional regulator genes,membrane transporter genes,efflux pump genes,and oxidation stress response genes,etc.The findings suggest that these genes play an important role in defense against the toxic effects of exposure to carbendazim and its metabolites. |
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