Enantioselective degradation of the organophosphorus insecticide isocarbophos in Cupriavidus nantongensis X1T: Characteristics, enantioselective regulation, degradation pathways, and toxicity assessment

The association of isocarbophos and isofenphos with different types of glucose metabolism: The role of inflammatory cells

To investigate the associations between isocarbophos and isofenphos with impaired fasting glucose (IFG) and type 2 diabetes mellitus (T2DM), and to assess the mediation roles of inflammation cells. There were 2701 participants in the case-control study, including 896 patients with T2DM, 900 patients with IFG, 905 subjects with NGT. Plasma isocarbophos and isofenphos concentrations were measured using gas chromatography and triple quadrupole tandem mass spectrometry. Generalized linear models were used to calculate the relationships between plasma isofenphos and isocarbophos levels with inflammatory factor levels and T2DM. Inflammatory cell was used as mediators to estimate the mediating effects on the above associations. Isocarbophos and isofenphos were positively related with T2DM after adjusting for other factors. The odds ratio (95% confidence interval) (OR (95%CI)) for T2DM was 1.041 (1.015, 1.068) and for IFG was 1.066 (1.009, 1.127) per unit rise in ln-isocarbophos. The prevalence of T2DM increased by 6.4% for every 1 unit more of ln-isofenphos (OR (95% CI): 1.064 (1.041, 1.087)). Additionally, a 100% rise in ln-isocarbophos was linked to 3.3% higher ln-HOMA2IR and a 0.029 mmol/L higher glycosylated hemoglobin (HbA1c) (95% CI: 0.007, 0.051). While a 100% rise in ln-isofenphos was linked to increase in ln-HOMA2 and ln-HOMA2IR of 5.8% and 3.4%, respectively. Furthermore, white blood cell (WBC) and neutrophilic (NE) were found to be mediators in the relationship between isocarbophos and T2DM, and the corresponding proportions were 17.12% and 17.67%, respectively. Isofenphos and isocarbophos are associated with IFG and T2DM in the rural Chinese population, WBC and NE have a significant role in this relationship.

Novel herbicide flusulfinam: absolute configuration, enantioseparation, enantioselective bioactivity, toxicity and degradation in paddy soils

BACKGROUND

Flusulfinam, a novel chiral herbicide, effectively controls Echinochloa crusgalli and Digitaria sanguinalis in paddy fields, indicating significant potential for practical agricultural applications. However, limited information is available on flusulfinam from a chiral perspective. A comprehensive evaluation of the enantiomeric levels of flusulfinam was performed.

RESULTS

Two enantiomers, R-(+)- and S-(-)-flusulfinam, were separately eluted using a Chiralcel OX-RH column. The bioactivity of R-flusulfinam against the two was 1.4-3.1 fold that of Rac-flusulfinam against two weed species. R-flusulfinam toxicity to Danio rerio larvae and Selenastrum capricornutumwere was 0.8- and 3.0-fold higher than Rac-flusulfinam, respectively. Degradation experiments were conducted using soil samples from four Chinese provinces. The findings indicated that S-flusulfinam (half-life T1/2 = 40.8 days) exhibits preferential degradation than R-flusulfinam (T1/2 = 46.2-57.8 days) in the soils of three provinces. Under anaerobic conditions, soil from Anhui exhibited preferential degradation of R-flusulfinam (T1/2 = 46.2 days) over S-flusulfinam (T1/2 = 63 days). Furthermore, two hydrolysis products of flusulfinam (M299 and M100) are proposed for the first time.

CONCLUSION

The enantioselective bioactivity, toxicity and degradation of flusulfinam were investigated. Our findings indicate that R-flusulfinam is an extremely effective and low-toxicity enantiomer for the tested species. The soil degradation test indicated that the degradation of flusulfinam was accelerated by higher organic matter content and lower soil pH. Furthermore, microbial communities may play a crucial role in driving the enantioselective degradation processes. This study lays the groundwork for the systematic evaluation of flusulfinam from an enantiomeric perspective. © 2024 Society of Chemical Industry.

Degradation of Isopyrazam in Soil: Kinetics, Microbial Mechanism, and Ecotoxicity of the Transformation Product

The degradation of isopyrazam in soils was investigated through kinetics, microbial contributions, and transformation products (TPs). Then the acute toxicity of isopyrazam and its TP to Chlorella pyrenoidosa was explored. The half-lives of isopyrazam in cinnamon soil, red soil, and black soil were 82.2, 141.7, and 120.3 days, respectively. A strain (Bacillus sp. A01) isolated from cinnamon soil could degrade 72.9% of isopyrazam at 10 mg/L after 6 days in a Luria-Bertani medium. Six TPs were observed with Bacillus sp. A01, and three of them were found in soil as well. Through the inhibition of cytochrome P450 enzymes, the production of oxidized isopyrazam was blocked. Microbial mediated hydroxylation, epoxidation, and dehydration were the main degradation pathways of isopyrazam. The acute toxicity results showed that the EC50 of 3-(difluoromethyl)-N-(9-(2-hydroxypropan-2-yl)-1,2,3,4-tetrahydro-1,4-methanonaphthalen-6-yl)-1-methyl-1H-pyrazole-4-carboxamide to Chlorella pyrenoidosa was 40 times higher than that of the parent. This work provides new insights for understanding the degradation behavior of isopyrazam in soil.

Characterization of two novel hydrolases from Sphingopyxis sp. DBS4 for enantioselective degradation of chiral herbicide diclofop-methyl

Diclofop-methyl, an aryloxyphenoxypropionate (AOPP) herbicide, is a chiral compound with two enantiomers. Microbial detoxification and degradation of various enantiomers is garnering immense research attention. However, enantioselective catabolism of diclofop-methyl has been rarely explored, especially at the molecular level. This study cloned two novel hydrolase genes (dcmA and dcmH) in Sphingopyxis sp. DBS4, and characterized them for diclofop-methyl degradation. DcmA, a member of the amidase superfamily, exhibits 26.1-45.9% identity with functional amidases. Conversely, DcmH corresponded to the DUF3089 domain-containing protein family (a family with unknown function), sharing no significant similarity with other biochemically characterized proteins. DcmA exhibited a broad spectrum of substrates, with preferential hydrolyzation of (R)-(+)-diclofop-methyl, (R)-(+)-quizalofop-ethyl, and (R)-(+)-haloxyfop-methyl. DcmH also preferred (R)-(+)-quizalofop-ethyl and (R)-(+)-haloxyfop-methyl degradation while displaying no apparent enantioselective activity towards diclofop-methyl. Using site-directed mutagenesis and molecular docking, it was determined that Ser175 was the fundamental residue influencing DcmA's activity against the two enantiomers of diclofop-methyl. For the degradation of AOPP herbicides, DcmA is an enantioselective amidase that has never been reported in research. This study provided novel hydrolyzing enzyme resources for the remediation of diclofop-methyl in the environment and deepened the understanding of enantioselective degradation of chiral AOPP herbicides mediated by microbes.

A study on the mechanism of the impact of phenthoate exposure on Prorocentrum lima

Extensive application of organophosphorus pesticides such as phenthoate results in its abundance in ecosystems, particularly in waterbodies, thereby providing the impetus to assess its role in aquatic organisms. However, the impact of phenthoate on marine algal physiological and proteomic response is yet to be explored despite its biological significance. In this study, we thus ought to investigate the impact of phenthoate in the marine dinoflagellate Prorocentrum lima, which is known for synthesizing okadaic acid (OA), the toxin responsible for diarrhetic shellfish poisoning (DSP). Our results showed that P. lima effectively absorbed phenthoate in seawater, with a reduction efficiency of 90.31% after 48 h. Surprisingly, the provision of phenthoate (100 and 1000 µg/L) substantially reduced the OA content of P. lima by 35.08% and 60.28% after 48 h, respectively. Meanwhile, phenthoate treatment significantly reduced the oxidative stress in P. lima. Proteomic analysis revealed that the expression level of seven crucial proteins involved in endocytosis was upregulated, suggesting that P. lima could absorb phenthoate via the endocytic signaling pathway. Importantly, phenthoate treatment resulted in the downregulation of proteins such as polyketide synthase (PKS)- 2, Cytochrome P450 (CYP450)- 1, and CYP450-2, involved in OA synthesis, thereby decreasing the OA biosynthesis by P. lima. Our results demonstrated the potential role of P. lima in the removal of phenthoate in water and exemplified the crucial proteins and their possible molecular mechanisms underpinning the phenthoate remediation by P. lima and also the regulatory role of phenthoate in restricting the OA metabolism. Collectively, these findings uncovered the synergistic mechanisms of phenthoate and P. lima in remediating phenthoate and reducing the toxic impact of P. lima.

Enantioselective Behaviors of Chiral Pesticides and Enantiomeric Signatures in Foods and the Environment

Unreasonable application of pesticides may result in residues in the environment and foods. Chiral pesticides consist of two or more enantiomers, which may exhibit different behaviors. This Review intends to provide progress on the enantioselective residues of chiral pesticides in foods. Among the main chiral analytical methods, high performance liquid chromatography (HPLC) is the most frequently utilized. Most chiral pesticides are utilized as racemates; however, due to enantioselective dissipation, bioaccumulation, biodegradation, and chiral conversion, enantiospecific residues have been found in the environment and foods. Some chiral pesticides exhibit strong enantioselectivity, highlighting the importance of evaluation on an enantiomeric level. However, the occurrence characteristics of chiral pesticides in foods and specific enzymes or transport proteins involved in enantioselectivity needs to be further investigated. This Review could help the production of some chiral pesticides to single-enantiomer formulations, thereby reducing pesticide consumption as well as increasing food production and finally reducing human health risks.

High-efficiency degradation of methomyl by the novel bacterial consortium MF0904: Performance, structural analysis, metabolic pathways, and environmental bioremediation

Methomyl is a widely used carbamate pesticide, which has adverse biological effects and poses a serious threat to ecological environments and human health. Several bacterial isolates have been investigated for removing methomyl from environment. However, low degradation efficiency and poor environmental adaptability of pure cultures severely limits their potential for bioremediation of methomyl-contaminated environment. Here, a novel microbial consortium, MF0904, can degrade 100% of 25 mg/L methomyl within 96 h, an efficiency higher than that of any other consortia or pure microbes reported so far. The sequencing analysis revealed that Pandoraea, Stenotrophomonas and Paracoccus were the predominant members of MF0904 in the degradation process, suggesting that these genera might play pivotal roles in methomyl biodegradation. Moreover, five new metabolites including ethanamine, 1,2-dimethyldisulfane, 2-hydroxyacetonitrile, N-hydroxyacetamide, and acetaldehyde were identified using gas chromatography-mass spectrometry, indicating that methomyl could be degraded firstly by hydrolysis of its ester bond, followed by cleavage of the C-S ring and subsequent metabolism. Furthermore, MF0904 can successfully colonize and substantially enhance methomyl degradation in different soils, with complete degradation of 25 mg/L methomyl within 96 and 72 h in sterile and nonsterile soil, respectively. Together, the discovery of microbial consortium MF0904 fills a gap in the synergistic metabolism of methomyl at the community level and provides a potential candidate for bioremediation applications.

Efficient Knocking Out of the Organophosphorus Insecticides Degradation Gene opdB in Cupriavidus nantongensis X1T via CRISPR/Cas9 with Red System

Cupriavidus nantongensis X1^T is a type strain of the genus Cupriavidus, that can degrade eight kinds of organophosphorus insecticides (OPs). Conventional genetic manipulations in Cupriavidus species are time-consuming, difficult, and hard to control. The clustered regularly interspaced short palindromic repeat (CRISPR)/associated protein 9 (Cas9) system has emerged as a powerful tool for genome editing applied in prokaryotes and eukaryotes due to its simplicity, efficiency, and accuracy. Here, we combined CRISPR/Cas9 with the Red system to perform seamless genetic manipulation in the X1^T strain. Two plasmids, pACasN and pDCRH were constructed. The pACasN plasmid contained Cas9 nuclease and Red recombinase, and the pDCRH plasmid contained the dual single-guide RNA (sgRNA) of organophosphorus hydrolase (OpdB) in the X1^T strain. For gene editing, two plasmids were transferred to the X1^T strain and a mutant strain in which genetic recombination had taken place, resulting in the targeted deletion of opdB. The incidence of homologous recombination was over 30%. Biodegradation experiments suggested that the opdB gene was responsible for the catabolism of organophosphorus insecticides. This study was the first to use the CRISPR/Cas9 system for gene targeting in the genus Cupriavidus, and it furthered our understanding of the process of degradation of organophosphorus insecticides in the X1^T strain.

Dissecting the Enantioselective Neurotoxicity of Isocarbophos: Chiral Insight from Cellular, Molecular, and Computational Investigations

Chiral organophosphorus pollutants are found abundantly in the environment, but the neurotoxicity risks of these asymmetric chemicals to human health have not been fully assessed. Using cellular, molecular, and computational toxicology methods, this story is to explore the static and dynamic toxic actions and its stereoselective differences of chiral isocarbophos toward SH-SY5Y nerve cells mediated by acetylcholinesterase (AChE) and further dissect the microscopic basis of enantioselective neurotoxicity. Cell-based assays indicate that chiral isocarbophos exhibits strong enantioselectivity in the inhibition of the survival rates of SH-SY5Y cells and the intracellular AChE activity, and the cytotoxicity of (S)-isocarbophos is significantly greater than that of (R)-isocarbophos. The inhibitory effects of isocarbophos enantiomers on the intracellular AChE activity are dose-dependent, and the half-maximal inhibitory concentrations (IC₅₀) of (R)-/(S)-isocarbophos are 6.179/1.753 μM, respectively. Molecular experiments explain the results of cellular assays, namely, the stereoselective toxic actions of isocarbophos enantiomers on SH-SY5Y cells are stemmed from the differences in bioaffinities between isocarbophos enantiomers and neuronal AChE. In the meantime, the modes of neurotoxic actions display that the key amino acid residues formed strong noncovalent interactions are obviously different, which are related closely to the molecular structural rigidity of chiral isocarbophos and the conformational dynamics and flexibility of the substrate binding domain in neuronal AChE. Still, we observed that the stable "sandwich-type π-π stacking" fashioned between isocarbophos enantiomers and aromatic Trp-86 and Tyr-337 residues is crucial, which notably reduces the van der Waals' contribution (ΔG_vdW) in the AChE-(S)-isocarbophos complexes and induces the disparities in free energies during the enantioselective neurotoxic conjugations and thus elucidating that (S)-isocarbophos mediated by synaptic AChE has a strong toxic effect on SH-SY5Y neuronal cells. Clearly, this effort can provide experimental insights for evaluating the neurotoxicity risks of human exposure to chiral organophosphates from macroscopic to microscopic levels.

Efficient biodegradation characteristics and detoxification pathway of organophosphorus insecticide profenofos via Cupriavidus nantongensis X1T and enzyme OpdB

Profenofos residues in the environment pose a high risk to mammals and non-target organisms. In this study, the biodegradation and detoxification of profenofos in an efficient degrading strain, Cupriavidus nantongensis X1^T, was investigated. Strain X1^T could degrade 88.82 % of 20 mg/L profenofos in 48 h. The optimum temperature and inoculation amount of strain X1^T for the degradation of profenofos were 30-37 °C and 20 % (V/V), respectively. Metabolic pathway analysis showed that strain X1^T could degrade both profenofos and its main metabolite 4-bromo-2-chlorophenol. Metabolite toxicity analysis results showed that dehalogenation was the main detoxification step in profenofos biodegradation. The key gene and enzyme for profenofos degradation in strain X1^T were also explored. RT-qPCR shows that organophosphorus hydrolase (OpdB) was the key enzyme to control the hydrolysis process in strain X1^T. The purified enzyme OpdB in vitro had the same degradation characteristics as strain X1^T. Divalent metal cations could significantly enhance the hydrolysis activity of strain X1^T and enzyme OpdB. Meanwhile, strain X1^T could degrade 60.89 % of 20 mg/L profenofos in actual field soil within 72 h. This study provides an efficient biological resource for the remediation of profenofos residual pollution in the environment.

Enantioselective toxicity, degradation and transformation of the chiral insecticide fipronil in two algae culture

The occurrence of pesticides and their metabolites in the environment can alter the ecological relationships between aquatic food chains. Fipronil is a broad-spectrum insecticide which release in the environment may harm the non-target organisms. However, the toxicity and biotransformation of its two enantiomers are far from fully understood. The present study aimed to investigate the aquatic toxicity and environmental behavior of fipronil at enantiomeric level using two freshwater algae, Scenedesmus quaclricauda (S. quaclricauda), and Chlorella vulgaris (C. vulgaris) through an integrative approach the transformation process of the individual enantiomer isolated and in racemic form. The 72 h-EC₅₀ values of rac-, R-, S-fipronil varied from 3.27 to 7.24 mg L^-1 with R-fipronil posing a more significant effect on algal growth inhibition. Chlorophyll a was more susceptible to fipronil exposure than chlorophyll b and carotenoids. Enantioselective alterations on physiological and biochemical parameters (chlorophyll a, chlorophyll b, carotenoids, and the activities of antioxidant enzyme catalase (CAT) and superoxide dismutase (SOD)) were also observed. The half-lives (T_1/2) of R-fipronil and S-fipronil in algae culture were 3.4-3.5 d and 4.0-4.9 d, respectively. By the end of the 17-d exposure, the enantiomer fractions (EFs) increased to 0.59, indicating a preferential depuration of R-fipronil. The metabolites monitoring showed the fipronil sulfide was the main metabolite followed by fipronil sulfone. The results revealed that the enantiomers of fipronil pose enantiospecific behaviors induced by these two algae, with the R-enantiomer more toxic to algal growth and favorable in degradation. These analyses are beneficial for understanding the ecological effect of chiral pesticide in aquatic environment, and the enantiomeric differences of the toxicity, degradation and the formation of toxic metabolites could be helpful for the eco-environmental risk evaluation.

Indigenous functional microbial communities for the preferential degradation of chloroacetamide herbicide S-enantiomers in soil

This study investigated indigenous functional microbial communities associated with the degradation of chloroacetamide herbicides acetochlor (ACE), S-metolachlor (S-MET) and their enantiomers in repeatedly treated soils. The results showed that biodegradation was the main process for the degradation of ACE, S-MET and their enantiomers. Eight dominant bacterial genera associated with the degradation were found: Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, Mycobacterium, Burkholderia, Afipia, and Kribbella. The S-enantiomers of ACE and S-MET were preferentially degraded, which mainly relied on Amycolatopsis, Saccharomonospora and Kribbella for the ACE S-enantiomer and Amycolatopsis and Saccharomonospora for the S-MET S-enantiomer. Importantly, the relative abundances of Amycolatopsis and Saccharomonospora increased by 146.3%-4467.2% in the S-enantiomer treatments of ACE and S-MET compared with the control, which were significantly higher than that in the corresponding R-enantiomer treatments (25.3%-4168.2%). Both metagenomic and qPCR analyses demonstrated that four genes, ppah, alkb, benA, and p450, were the dominant biodegradation genes (BDGs) potentially involved in the preferential degradation of the S-enantiomers of ACE and S-MET. Furthermore, network analysis suggested that Amycolatopsis, Saccharomonospora, Mycoplasma, Myroides, and Mycobacterium were the potential hosts of these four BDGs. Our findings indicated that Amycolatopsis and Saccharomonospora might play pivotal roles in the preferential degradation of the S-enantiomers of ACE and S-MET.

Old pesticide, new use: Smart and safe enantiomer of isocarbophos in locust control

Locust plagues are still worldwide problems. Selecting active enantiomers from current chiral insecticides is necessary for controlling locusts and mitigating the pesticide pollution in agricultural lands. Herein, two enantiomers of isocarbophos (ICP) were separated and the enantioselectivity in insecticidal activity against the pest Locusta migratoria manilensis (L. migratoria) and mechanisms were investigated. The significant difference of LD₅₀ between (+)-ICP (0.609 mg/kg bw) and (-)-ICP (79.412 mg/kg bw) demonstrated that (+)-ICP was a more effective enantiomer. The enantioselectivity in insecticidal activity of ICP enantiomers could be attributed to the selective affinity to acetylcholinesterase (AChE). Results of in vivo and in vitro assays suggested that AChE was more sensitive to (+)-ICP. In addition, molecular docking showed that the -CDOKER energies of (+)-ICP and (-)-ICP were 25.6652 and 24.4169, respectively, which suggested a stronger affinity between (+)-ICP and AChE. Significant selectivity also occurred in detoxifying enzymes activities (carboxylesterases (CarEs) and glutathione S-transferases (GSTs)) and related gene expressions. Suppression of detoxifying enzymes activities with (+)-ICP treatment suggested that (-)-ICP may induce the detoxifying enzyme-mediated ICP resistance. A more comprehensive understanding of the enantioselectivity of ICP is necessary for improving regulation and risk assessment of ICP.