Isolation and Characterization of the Pymetrozine-Degrading Strain Pseudomonas sp. BYT-1

Enantioselective Metabolism of Chiral Fungicide Prothioconazole by Mycobacterium sp. Y-3 and Its Bioaugmentation

Prothioconazole (PTC) is a kind of chiral triazole fungicide widely used in agricultural production, which can easily cause residual contamination and chiral selective toxicity. Microorganisms are the main participants involved in pollutant degradation in the environment. However, studies on the microbial enantioselective degradation of PTC and bioaugmentation of PTC-contaminated soil are still scarce. Herein, we isolated an efficient PTC-degrading strain, Mycobacterium sp. Y-3. Strain Y-3 preferentially metabolized (R)-PTC over (S)-PTC; the degradation rate of (R)-PTC was 2.5 times that of (S)-PTC. The T1/2 values of 20-80 μM (Rac)-/(S)-/(R)-PTC after treatment with strain Y-3 were 4.1-7.1 h at 37 °C and pH 5.0. The addition of glutamine could significantly enhance the PTC degradation ability of strain Y-3. Strain Y-3 metabolized PTC via methylation to form prothioconazole-S-methyl, the detoxification pathway for PTC. In bioaugmentation experiments, strain Y-3 eliminated PTC residues in the soil within 12 days. High-throughput sequencing analysis indicated that strain Y-3 colonized well in the soil. Inoculation with strain Y-3 reduced soil microbial community diversity and richness, while the bioaugmentation treatment enhanced the soil microbial community associations. These findings provide new insights into the enantioselective microbial metabolism of chiral PTC and in situ bioaugmentation of PTC-contaminated soils.

A stress-tolerant strain Rhodococcus sp. WH103 was isolated and co-immobilized to more efficiently degrade phenazine-1-carboxylic acid

Phenazine-1-carboxylic acid (PCA), the main active ingredient of the bio-fungicide shenqinmycin, has been widely used in agriculture due to its excellent antimicrobial properties. However, it poses risks to non-target microorganisms and causes phytotoxicity, necessitating efficient degradation strategies. In this study, six PCA-degrading bacterial strains were isolated from the rice rhizosphere by enrichment culture. Subsequently, Rhodococcus sp. WH103, which showed the highest efficiency in degrading PCA as well as tolerance to high temperature (42 °C) and osmotic stress (addition of 0.7 M NaCl) was subjected to further study. Additionally, the co-immobilization of strain WH103 cells with sodium alginate (SA) and biochar was explored. The SA-biochar-bacterial beads successfully degraded PCA to below 0.001 mM under optimized conditions within 21 h and exhibited reusability for up to 12 cycles. Notably, the SA-biochar-bacterial beads significantly alleviated the phytotoxicity of PCA during seed germination. This study provides an excellent strain resource and method reference for PCA degradation, lays the foundation for the practical application of pollutant-degrading microorganisms in environmental remediation.

Microbial degradation mechanism and pathway of the insecticide thiamethoxam by isolated Bacillus Cereus from activated sludge

The high water solubility and ecotoxicity of thiamethoxam (TMX) is a potential hazard to ecosystems and human health. Here, a strain of Bacillus cereus with high TMX degradation activity was isolated from the sediment of the A2O process in the wastewater treatment plant and was able to utilize TMX as its sole carbon source. Under different environmental conditions, the degradation efficiency of TMX by Bacillus cereus-S1 (strain S1) ranged from 41.0% to 68.9% after 216 h. The optimum degradation conditions were DO = 3.5 mg/L and pH 9.0. The addition of an appropriate carbon-to-nitrogen ratio could accelerate the degradation of TMX. A plausible biodegradation pathway has been proposed based on the identified metabolites and their corresponding degradation pathways. TMX can be directly converted into Clothianidin (CLO), TMX-dm-hydroxyl and TMX-Urea by a series of reactions such as demethylation, oxadiazine ring cleavage and C=N substitution by hydroxy group. The main products were TMX-dm-hydroxyl and TMX-Urea, the amount of CLO production is relatively small. This study aims to provide a new approach for efficient degradation of TMX; furthermore, strain S1 is a promising biological source for in situ remediation of TMX contamination.

Biosynthesis of poly(3-hydroxybutyrate) by N,N-dimethylformamide degrading strain Paracoccus sp. PXZ: A strategy for resource utilization of pollutants

N,N-dimethylformamide is a toxic chemical solvent, which widely exists in industrial wastewater. Nevertheless, the relevant methods merely achieved non-hazardous treatment of N,N-dimethylformamide. In this study, one efficient N,N-dimethylformamide degrading strain was isolated and developed for pollutant removal coupling with poly(3-hydroxybutyrate) (PHB) accumulation. The functional host was characterized as Paracoccus sp. PXZ, which could consume N,N-dimethylformamide as the nutrient substrate for cell reproduction. Whole-genome sequencing analysis confirmed that PXZ simultaneously possesses the essential genes for poly(3-hydroxybutyrate) synthesis. Subsequently, the approaches of nutrient supplementation and various physicochemical variables to strengthen poly(3-hydroxybutyrate) production were investigated. The optimal biopolymer concentration was 2.74 g·L^-1 with a poly(3-hydroxybutyrate) proportion of 61%, showing a yield of 0.29 g-PHB·g^-1-fructose. Furthermore, N,N-dimethylformamide served as the special nitrogen matter that could realize a similar poly(3-hydroxybutyrate) accumulation. This study provided a fermentation technology coupling with N,N-dimethylformamide degradation, offering a new strategy for resource utilization of specific pollutants and wastewater treatment.

Covalent Organic Framework-Semiconductor-Based Heterostructures for Photocatalytic Applications

Photocatalysis is a promising and sustainable technology in the fields of energy conversion/storage and environment purification; however, the utilization of individual component as photocatalyst is generally restricted due to the low catalytic activity deriving from the rapid recombination of photogenerated electrons/holes. Covalent organic framework (COF)-semiconductor-based composite photocatalysts with synergistic effects provide a feasible route to achieve high-performance photocatalytic reactions with more active sites, strong light utilization ability, and high stability. In recent years, significant progress has been made in the rational design and preparation of the COF-semiconductors-based heterostructures for photocatalytic water splitting, carbon dioxide (CO₂ ) reduction, and dye/pollutant degradation. In this Review, the synthetic strategies of COF-semiconductor-based heterostructures are first introduced, which includes the rational design of the morphology, connection modes, and type of heterojunctions. The performance of COF-semiconductor-based heterostructures in different photocatalytic reactions are comprehensively reviewed. The structure-activity relationship and the synergistic effects within the heterostructures are discussed, and the photocatalytic mechanism and the role of COFs during the photocatalytic process are also presented. Finally, an outlook and challenges of realizing COF-semiconductor-based heterostructures with simple synthesis methods, diverse functions, high performance, and well-defined reaction mechanisms are provided.

Characterization and catalytic mechanism of a direct demethylsulfide hydrolase for catabolism of the methylthiol-s-triazine prometryn

Demethylthio is one of the most important ways for microorganisms to metabolize triazine herbicides. Previous studies have found that the initial reaction of prometryn catabolism in Leucobacter triazinivorans JW-1 was the hydroxylation of its methylthio group, however, the corresponding functional enzyme was not yet clear. In this study, the gene proA was responsible for the initial step of prometryn catabolism from the strain JW-1 was cloned and expressed, and the purified amidohydrolases ProA have the ability to transform prometryn to 2-hydroxypropazine and methanethiol. The optimized reaction temperature and pH of ProA were 45 °C and 7.0, respectively, and the kinetic constants K_m and V_max of ProA for the catalysis of prometryn were 32.6 μM and 0.09 μmol/min/mg, respectively. Molecular docking analyses revealed that different catalysis efficiency of ProA and TrzN (Nocardioides sp. C190) for prometryn and atrazine was due to non-covalent changes in amino acid residues. Our findings provide new insights into the understanding of s-triazine catabolism at the molecular level.

Effects of Pymetrozine and Tebuconazole with Foliar Fertilizer Through Mixed Application on Plant Growth and Pesticide Residues in Cucumber

The mixed application of pesticides and foliar fertilizer has been widely used in the production of cucumber, however, their effects on plant growth and pesticide dissipation are still unclear. In this study, the effects of mixed application of pymetrozine, tebuconazole and foliar fertilizer on the cucumber plant growth and pesticide dissipation were investigated simultaneously. The results show that the mixed use of pymetrozine, tebuconazole, especially adding foliar fertilizer, improved the physiological indexes (i.e., area, nitrogen content and chlorophyll content of the leaves, and root growth) of cucumber plants compared to those with the application of single pesticide. Meanwhile, it can significantly affect the dissipation of pymetrozine even in the slower growth matrices (lower leaves, stems, and plants). The residue of tebuconazole in cucumber plants was affected by the combination of formulation type and foliar fertilizer. This study can provide data for scientifically guiding the mixed application of pesticide and fertilizer.

A novel hydrolase PyzH catalyses the cleavage of C=N double bond for pymetrozine degradation in Pseudomonas sp. BYT-1

Pymetrozine is a synthetic pesticide that can be utilized as the sole carbon source by Pseudomonas sp. strain BYT-1. However, the genes involved in the degradation of pymetrozine remain unknown. We used transposon mutagenesis to create a mutant that unable to hydrolyze pymetrozine. The transposon interrupted the gene pyzH, which was cloned by self-formed adaptor PCR. PyzH hydrolyzed the C=N double bond of pymetrozine to produce 4-amino-6-methyl-4,5-dihydro-2H-[1,2,4]triazin-3-one (AMDT) and nicotinaldehyde; the latter inhibits PyzH activity. PyzH can completely hydrolyze pymetrozine in the presence of dehydrogenase ORF6, which can convert nicotinaldehyde into nicotinic acid and relieve the inhibition. H₂ ¹⁸ O-labeling experiments showed that the oxygen atom of nicotinaldehyde came from water instead of oxygen. PyzH homologous genes were also found in other soil isolates able to degrade pymetrozine.

Isolation and identification of a novel erythromycin-degrading fungus, Curvularia sp. RJJ-5, and its degradation pathway

Erythromycin pollution is an important risk to the ecosystem and human health worldwide. Thus, it is urgent to develop effective approaches to decontaminate erythromycin. In this study, we successfully isolated a novel erythromycin-degrading fungus from an erythromycin-contaminated site. The erythromycin biodegradation characteristics were investigated in mineral salt medium with erythromycin as the sole carbon and energy source. The metabolites of erythromycin degraded by fungus were identified and used to derive the degradation pathway. Based on morphological and phylogenetic analyses, the isolated strain was named Curvularia sp. RJJ-5 (MN759651). Optimal degradation conditions for strain RJJ-5 were 30°C, and pH 6.0 with 100 mg L-1 erythromycin substrate. The strain could degrade 75.69% erythromycin under this condition. The following metabolites were detected: 3-depyranosyloxy erythromycin A, 7,12-dyhydroxy-6-deoxyerythronolide B, 2,4,6,8,10,12-hexamethyl-3,5,6,11,12,13-hexahydroxy-9-ketopentadecanoic acid and cladinose. It was deduced that the erythromycin A was degraded to 3-depyranosyloxy erythromycin A by glycoside hydrolase in the initial reaction. These results imply that Curvularia sp. RJJ-5 is a novel erythromycin-degrading fungus that can hydrolyze erythromycin using a glycoside hydrolase and has great potential for removing erythromycin from mycelial dreg and the contaminated environment.

Effects of pesticide residues on bacterial community diversity and structure in typical greenhouse soils with increasing cultivation years in Northern China

The understanding of soil microbiome is important for sustainable cultivation, especially under greenhouse conditions. Here, we investigated the changes in soil pesticide residues and microbial diversity and community structure at different cultivation years under a greenhouse system. The 9-to-14 years sites were found to have the least diversity/rich microbial population as compared to sites under 8 years and over 16 years, as analyzed with alpha diversity index. In total, 42 bacterial phyla were identified across soils with different pesticide residues and cultivation ages. Proteobacteria, Acidobacteria, and Bacteroidetes represented the dominant phyla, that accounted for 34.2-43.4%, 9.7-19.3% and 9.2-16.5% of the total population, respectively. Our data prove that certain pesticides contribute to variation in soil microbial community and that soil bacteria respond differently to cultivation years under greenhouse conditions. Thus, this study provides an insight into microbial community structure changes by pesticides under greenhouse systems and natural biodegradation may have an important part in pesticides soil decontamination.

An angular dioxygenase gene cluster responsible for the initial phenazine-1-carboxylic acid degradation step in Rhodococcus sp. WH99 can protect sensitive organisms from toxicity

A bacterial strain, Rhodococcus sp. WH99, capable of degrading phenazine-1-carboxylic acid (PCA) was isolated and characterized. Genome comparison revealed that a 21499-bp DNA fragment containing a putative angular dioxygenase gene cluster consisting of the dioxygenase-, ferredoxin reductase- and ferredoxin-encoding genes (pzcA1A2, pzcC and pzcD) is missed in the PCA degradation-deficient mutant WH99M. The pzcA1A2CD genes were expressed in Escherichia coli respectively and hydroxylation of PCA to 1,2-dihydroxyphenazine occurred in vitro only when all components were present. However, in vivo analyses showed that pzcA1A2 and pzcD were indispensable for PCA degradation, while PzcC can be partially replaced by other ferredoxin reductases. Hydroxylation of PCA not only initiates degradation of PCA in strain WH99 but also provides protection to sensitive organisms that would otherwise be inhibited by PCA toxicity. This study illustrates a new initial PCA degradation step in Gram-positive bacteria and enhances our understanding of the genes responsible for PCA hydroxylation, thus enabling targeted studies on protection by PCA degradation in diverse environments.

Identification of the key amino acid sites of the carbofuran hydrolase CehA from a newly isolated carbofuran-degrading strain Sphingbium sp. CFD-1

A novel carbofuran-degrading strain CFD-1 was isolated and preliminarily identified as Sphingbium sp. This strain was able to utilize carbofuran as the sole carbon source for growth. The carbofuran hydrolase gene cehA was cloned from strain CFD-1 and expressed in Escherichia coli. CehA could hydrolyze carbamate pesticides including carbofuran and carbaryl efficiently, while it showed poor hydrolysis ability against isoprocarb, propoxur, oxamyl and aldicarb. CehA displayed maximal enzymatic activity at 40 °C and pH 7.0. The apparent Km and Kcat values of CehA for carbofuran were 133.22 ± 5.70 μM and 9.48 ± 0.89 s-1, respectively. The site-directed mutation experiment showed that His313, His315, His453 and His495 played important roles in the hydrolysis of carbofuran by CehA. Furthermore, the sequence of cehA is highly conserved among different carbofuran-degrading strains, and there are mobile elements around cehA, indicating that it may be transferred horizontally between different strains.