Dataset Information

A Novel Pathway of Chlorimuron-Ethyl Biodegradation by Chenggangzhangella methanolivorans Strain CHL1 and Its Molecular Mechanisms.

ABSTRACT: Chlorimuron-ethyl is a widely used herbicide in agriculture. However, uncontrolled chlorimuron-ethyl application causes serious environmental problems. Chlorimuron-ethyl can be effectively degraded by microbes, but the underlying molecular mechanisms are not fully understood. In this study, we identified the possible pathways and key genes involved in chlorimuron-ethyl degradation by the Chenggangzhangella methanolivorans strain CHL1, a Methylocystaceae strain with the ability to degrade sulfonylurea herbicides. Using a metabolomics method, eight intermediate degradation products were identified, and three pathways, including a novel pyrimidine-ring-opening pathway, were found to be involved in chlorimuron-ethyl degradation by strain CHL1. Transcriptome sequencing indicated that three genes (atzF, atzD, and cysJ) are involved in chlorimuron-ethyl degradation by strain CHL1. The gene knock-out and complementation techniques allowed for the functions of the three genes to be identified, and the enzymes involved in the different steps of chlorimuron-ethyl degradation pathways were preliminary predicted. The results reveal a previously unreported pathway and the key genes of chlorimuron-ethyl degradation by strain CHL1, which have implications for attempts to enrich the biodegradation mechanism of sulfonylurea herbicides and to construct engineered bacteria in order to remove sulfonylurea herbicide residues from environmental media.

SUBMITTER: Yu Z

PROVIDER: S-EPMC9456165 | biostudies-literature | 2022 Aug

REPOSITORIES: biostudies-literature

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A Novel Pathway of Chlorimuron-Ethyl Biodegradation by <i>Chenggangzhangella methanolivorans</i> Strain CHL1 and Its Molecular Mechanisms.

Yu Zhixiong Z Dai Yumeng Y Li Tingting T Gu Wu W Yang Yi Y Li Xiang X Peng Pai P Yang Lijie L Li Xinyu X Wang Jian J Su Zhencheng Z Li Xu X Xu Mingkai M Zhang Huiwen H

International journal of molecular sciences 20220831 17

Chlorimuron-ethyl is a widely used herbicide in agriculture. However, uncontrolled chlorimuron-ethyl application causes serious environmental problems. Chlorimuron-ethyl can be effectively degraded by microbes, but the underlying molecular mechanisms are not fully understood. In this study, we identified the possible pathways and key genes involved in chlorimuron-ethyl degradation by the <i>Chenggangzhangella methanolivorans</i> strain CHL1, a Methylocystaceae strain with the ability to degrade ...[more]

PMID: 36077288

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Project description:Chlorimuron-ethyl is a commonly used sulfonylurea herbicide, and its long-term residues cause serious environmental problems. Biodegradation of chlorimuron-ethyl is effective and feasible, and many degrading strains have been obtained, but still, the genes and enzymes involved in this degradation are often unclear. In this study, whole-genome sequencing was performed on chlorimuron-ethyl-degrading strain, Chenggangzhangella methanolivorans CHL1. The complete genome of strain CHL1 contains one circular chromosome of 5,542,510 bp and a G+C content of 68.17 mol%. Three genes, sulE, pnbA, and gst, were predicted to be involved in the degradation of chlorimuron-ethyl, and this was confirmed by gene knockout and gene complementation experiments. The three genes were cloned and expressed in Escherichia coli BL21 (DE3) to allow for the evaluation of the catalytic activities of the respective enzymes. The glutathione-S-transferase (GST) catalyzes the cleavage of the sulfonylurea bridge of chlorimuron-ethyl, and the esterases, PnbA and SulE, both de-esterify it. This study identifies three key functional genes of strain CHL1 that are involved in the degradation of chlorimuron-ethyl and also provides new approaches by which to construct engineered bacteria for the bioremediation of environments polluted with sulfonylurea herbicides. IMPORTANCE Chlorimuron-ethyl is a commonly used sulfonylurea herbicide, worldwide. However, its residues in soil and water have a potent toxicity toward sensitive crops and other organisms, such as microbes and aquatic algae, and this causes serious problems for the environment. Microbial degradation has been demonstrated to be a feasible and promising strategy by which to eliminate xenobiotics from the environment. Many chlorimuron-ethyl-degrading microorganisms have been reported, but few studies have investigated the genes and enzymes that are involved in the degradation. In this work, two esterase-encoding genes (sulE, pnbA) and a glutathione-S-transferase-encoding gene (gst) responsible for the detoxification of chlorimuron-ethyl by strain Chenggangzhangella methanolivorans CHL1 were identified, then cloned and expressed in Escherichia coli BL21 (DE3). These key chlorimuron-ethyl-degrading enzymes are candidates for the construction of engineered bacteria to degrade this pesticide and enrich the resources for bioremediating environments polluted with sulfonylurea herbicides.

Project description:Excessive application of the herbicide chlorimuron-ethyl (CE) severely harms subsequent crops and poses severe risks to environmental health. Therefore, methods for efficiently decreasing and eliminating CE residues are urgently needed. Microbial consortia show potential for bioremediation due to their strong metabolic complementarity and synthesis. In this study, a microbial consortium entitled L1 was enriched from soil contaminated with CE by a "top-down" synthetic biology strategy. The consortium could degrade 98.04% of 100 mg L-1 CE within 6 days. We characterized it from the samples at four time points during the degradation process and a sample without degradation activity via metagenome and 16S rDNA sequencing. The results revealed 39 genera in consortium L1, among which Methyloversatilis (34.31%), Starkeya (28.60%), and Pseudoxanthomonas (7.01%) showed relatively high abundances. Temporal succession and the loss of degradability did not alter the diversity and community composition of L1 but changed the community structure. Taxon-functional contribution analysis predicted that glutathione transferase [EC 2.5.1.18], urease [EC 3.5.1.5], and allophanate hydrolase [EC 3.5.1.54] are relevant for the degradation of CE and that Methyloversatilis, Pseudoxanthomonas, Methylopila, Hyphomicrobium, Stenotrophomonas, and Sphingomonas were the main degrading genera. The degradation pathway of CE by L1 may involve cleavage of the CE carbamide bridge to produce 2-amino-4-chloro-6-methoxypyrimidine and ethyl o-sulfonamide benzoate. The results of network analysis indicated close interactions, cross-feeding, and co-metabolic relationships between strains in the consortium, and most of the above six degrading genera were keystone taxa in the network. Additionally, the degradation of CE by L1 required not only "functional bacteria" with degradation capacity but also "auxiliary bacteria" without degradation capacity but that indirectly facilitate/inhibit the degradation process; however, the abundance of "auxiliary bacteria" should be controlled in an appropriate range. These findings improve the understanding of the synergistic effects of degrading bacterial consortia, which will provide insight for isolating degrading bacterial resources and constructing artificial efficient bacterial consortia. Furthermore, our results provide a new route for pollution control and biodegradation of sulfonylurea herbicides.

Dataset Information

A Novel Pathway of Chlorimuron-Ethyl Biodegradation by Chenggangzhangella methanolivorans Strain CHL1 and Its Molecular Mechanisms.

Publications

A Novel Pathway of Chlorimuron-Ethyl Biodegradation by <i>Chenggangzhangella methanolivorans</i> Strain CHL1 and Its Molecular Mechanisms.

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