Semi-rational design for enhancing thermostability of Culex pipiens acetylcholinesterase and sensitivity analysis of acephate.

Acetylcholinesterase (AChE) has emerged as a significant biological recognition element in the biosensor field, particularly for the detection of insecticides. Nevertheless, the weak thermostability of AChE restricts its utilization due to the complexities associated with production, storage, and application environments. By evaluating the binding affinity between representative AChE and insecticides, an AChE from Culex pipiens was screened out, which displayed a broad-spectrum and high sensitivity to insecticides. The C. pipiens AChE (CpA) was subsequently expressed in Escherichia coli (E. coli) as a soluble active protein. Furthermore, a three-point mutant, M4 (A340P/D390E/S581P), was obtained using a semi-rational design strategy that combined molecular dynamics (MD) simulation and computer-aided design, which exhibited a four-fold increase in half-life at 40 °C compared to the wild-type (WT) enzyme. The mutant M4 also demonstrated an optimal temperature of 50 °C and a melting temperature (Tm) of 51.2 °C. Additionally, the sensitivity of WT and M4 to acephate was examined, revealing a 50-fold decrease in the IC50 value of M4. The mechanism underlying the improvement in thermal performance was elucidated through secondary structure analysis and MD simulations, indicating an increase in the proportion of protein helices and local structural rigidity. MD analysis of the protein-ligand complexes suggested that the enhanced sensitivity of M4 could be attributed to frequent specific contacts between the organophosphorus (OP) group of acephate and the key active site residue Ser327. These findings have expanded the possibilities for the development of more reliable and effective industrial enzyme preparations and biosensors.

Insecticide Susceptibilities and Enzyme Activities of Four Stink Bug Populations in Mississippi, USA.

In Mississippi, the Pentatomidae complex infesting soybean is primarily composed of Euschistus servus, Nezara viridula, Chinavia hilaris, and Piezodorus guildinii. This study employed spray bioassays to evaluate the susceptibilities of these stink bugs to seven commonly used formulated insecticides: oxamyl, acephate, bifenthrin, λ-cyhalothrin, imidacloprid, thiamethoxam, and sulfoxaflor. Stinks bugs were collected from soybeans in Leland, MS, USA during 2022 and 2023, as well as from wild host plants in Clarksdale, MS. There was no significant difference in the susceptibility of C. hilaris to seven insecticides between two years, whereas P. guildinii showed slightly increased susceptibility to neonicotinoids in 2023. Among all four stink bug species, susceptibility in 2022 was ranked as P. guildinii ≤ C. hilaris ≈ N. viridula, while in 2023, it was ranked as P. guildinii ≤ C. hilaris ≤ E. Servus. Additionally, populations of E. servus and P. guildinii collected from Clarksdale exhibited high tolerance to pyrethroids and neonicotinoids. Moreover, populations of E. servus and P. guildinii from SIMRU-2022 and Clarksdale-2023 showed elevated esterase and cytochrome P450 activity, respectively. These findings from spray bioassays and enzyme activity analyses provide a baseline for monitoring insecticide resistance in Pentatomidae and can guide insecticide resistance management strategies for Mississippi soybean.

Ephedra alata Seeds Confer Kidney Protection against Early Life Exposure to Acephate by Regulating Oxidative Insult and Activating Autophagy.

The aim of the current work was to examine for the first time the nephropreventive capacity of Ephedra alata seed extract (E) against maternal exposure to acephate in rat offspring. The in vivo results revealed that E. alata supplementation for 28 days (40 mg/kg b.w.) significantly attenuated the nephrotoxicity in adult offspring induced by acephate. In fact, it decreased the levels of creatinine and uric acid and increased the albumin content compared to the intoxicated group. The in utero studies showed that E. alata inhibited the renal oxidative stress generated by acephate exposure by reducing lipid peroxidation and enhancing antioxidant biomarker activities (GSH, CAT, and SOD). The inhibition of DNA fragmentation and the improvement of the ultrastructural changes highlighted the prophylactic effect of E. alata in renal tissue. Additionally, the immunofluorescence study showed the upregulation of LC3 gene expression, suggesting the capacity of E. alata extract to stimulate autophagic processes as a protective mechanism. Molecular docking analysis indicated that hexadecasphinganine, the major compound in E. alata, has a higher affinity toward the Na+/K+-ATPase, epithelial sodium channel (ENaC), and sodium hydrogen exchanger 3 (NHE3) genes than acephate. Hexadecasphinganine could be considered a potential inhibitor of the activity of these genes and therefore exerted its preventive capacity. The obtained findings confirmed that E. alata seed extract exerted nephropreventive capacities, which could be related to its bioactive compounds, which possess antioxidant activities.

Suspected intermediate syndrome in a dog after organophosphate poisoning.

OBJECTIVE: To discuss the clinical presentation and successful treatment of a suspected case of intermediate syndrome due to organophosphate (OP) poisoning in a dog. CASE SUMMARY: Two dogs presented with acute cholinergic signs after ingesting an OP insecticide containing 50% acephate. Clinical signs consistent with acute cholinergic crisis resolved in both dogs within 24 hours postingestion. One dog developed an onset of neurological signs consistent with intermediate syndrome approximately 24 hours postingestion. This patient's clinical signs resolved with the use of pralidoxime chloride. NEW OR UNIQUE INFORMATION PROVIDED: OP poisoning most commonly presents as an acute cholinergic crisis, with rare instances of animals developing intermediate syndrome. Few reports of successful treatment and recovery from intermediate syndrome exist in the veterinary literature, particularly with instances in which 2 dogs within the same exposure setting were treated for acute cholinergic signs and only 1 progressed to an intermediate syndrome. This report also highlights the importance of early intervention with pralidoxime chloride prior to the onset of aging.

Early-life exposure to acephate inhibits sexual development and induces testicular and ovarian toxicity in mice.

Acephate is an organophosphate insecticide that exerts its toxicity by acting on the nervous system of insects. In addition to its action on the mammalian nervous system, acephate can also induce endocrine disruption of the reproductive system in mammals. However, the effects of acephate on sexual maturation and ovary development remain unclear. This study evaluated whether early-life exposure to acephate negatively impacts the male and female sexual maturation process and mature reproductive tissues. C57BL/6N mice were exposed to acephate (0, 0.3, 300 ppm) in drinking water from embryonic day 11.5 to ablactation, when the pups were four weeks old. Both sexes in the high-dose group experienced an early postnatal growth deficit, while females in the low-dose group continued to gain weight until 10 weeks of age. Exposure to acephate altered the anogenital index in females. Furthermore, preputial separation and vaginal opening were delayed in the high-dose group. At maturity, the weight of the seminal vesicles was decreased in the high-dose group. All treated groups exhibited increased vacuolation, accumulation of residual bodies, and degeneration in the testes. Furthermore, follicle regression was observed, and the healthy follicle number at each developmental stage was decreased in all treated groups. These results are probably due to the inhibition of the regulation by the hypothalamic-pituitary-gonadal axis and direct toxicity to reproductive organs. In conclusion, our study demonstrates that early-life exposure to acephate in mice may disrupt normal postnatal development, postpone puberty onset, and adversely affect reproductive functions during the reproductive period in both sexes.

Dissipation kinetics, residue determination and consumer risk assessment of acephate on green pea by gas chromatography-electron capture detector.

The present study on "acephate persistence on green pea" was conducted in SKUAST-Kashmir. The study aimed to determine the persistence, dissipation kinetics and waiting period of acephate on green pea. Acephate was sprayed at 75% soluble powder (SP) at 560 g a.i.ha-1 at the fruiting stage followed by another application at a 10 day interval. A rapid and accurate method (quick, easy, cheap, effective, rugged and safe, QuEChERS) was used for extraction and the residue was determined by gas chromatography-electron capture detection on a CPSIL-8CB capillary column (0.25um film thickness, 0.25 mm i.d, 30 m length). At the fortification levels of 0.05, 0.1 and 0.5 mg kg-1 , the percentage recovery of acephate on green pea was found in the range of 71-107%. The initial deposit of green pea was estimated to be 0.37 mg kg-1 . At the indicated dose, the residue of acephate on green pea dissipated below the limit of quantification of 0.05 mg kg-1 after 10 days. Acephate degradation was quick in green pea, with a half-life of 4.07 days. For safe eating of green peas, a 10 day waiting period is recommended. The gas chromatography-electron capture detection technique was validated by following the SANTE standards.

Surface-enhanced Raman spectroscopy charged probes under inverted superhydrophobic platform for detection of agricultural chemicals residues in rice combined with lightweight deep learning network.

In this study, surface-enhanced Raman spectroscopy (SERS) charged probes and an inverted superhydrophobic platform were used to develop a detection method for agricultural chemicals residues (ACRs) in rice combined with lightweight deep learning network. First, positively and negatively charged probes were prepared to adsorb ACRs molecules to SERS substrate. An inverted superhydrophobic platform was prepared to alleviate the coffee ring effect and induce tight self-assembly of nanoparticles for high sensitivity. Chlormequat chloride of 15.5-0.05 mg/L and acephate of 100.2-0.2 mg/L in rice were measured with the relative standard deviation of 4.15% and 6.25%. SqueezeNet were used to develop regression models for the analysis of chlormequat chloride and acephate. And the excellent performances were obtained with the coefficients of determination of prediction of 0.9836 and 0.9826 and root-mean-square errors of prediction of 0.49 and 4.08. Therefore, the proposed method can realize sensitive and accurate detection of ACRs in rice.

Rapid Biodegradation of the Organophosphorus Insecticide Acephate by a Novel Strain Burkholderia sp. A11 and Its Impact on the Structure of the Indigenous Microbial Community.

The acephate-degrading microbes that are currently available are not optimal. In this study, Burkholderia sp. A11, an efficient degrader of acephate, presented an acephate-removal efficiency of 83.36% within 56 h (100 mg·L-1). The A11 strain has a broad substrate tolerance and presents a good removal effect in the concentration range 10-1600 mg·L-1. Six metabolites from the degradation of acephate were identified, among which the main products were methamidophos, acetamide, acetic acid, methanethiol, and dimethyl disulfide. The main degradation pathways involved include amide bond breaking and phosphate bond hydrolysis. Moreover, strain A11 successfully colonized and substantially accelerated acephate degradation in different soils, degrading over 90% of acephate (50-200 mg·kg-1) within 120 h. 16S rDNA sequencing results further confirmed that the strain A11 gradually occupied a dominant position in the soil microbial communities, causing slight changes in the diversity and composition of the indigenous soil microbial community structure.

Maternal Exposure to Acephate Caused Nephrotoxicity in Adult Offspring Rats Mediated by Excessive Autophagy Activation, Oxidative Stress Induction, and Altered Epithelial Sodium Channel and Na+/K+-ATPase Gene Expression.

This study examined how maternal exposure to acephate-an organophosphate-based insecticide-affected the renal development in rat offspring during adulthood. Virgin female Wistar rats were randomly allocated to three groups: group 1 (control) received sterile water; groups 2 and 3 were intragastrically exposed to low (14 mg/kg) and high (28 mg/kg) doses of acephate from day 6 of pregnancy until delivery, respectively. Further, the offspring of the adult female rats were euthanized in postnatal week 8. Compared with the controls, the adult rat offspring with exposure to low and high doses of acephate exhibited elevated plasma creatinine and blood urea nitrogen levels. Additionally, immunofluorescence analysis revealed the upregulation of autophagic marker genes (Beclin-1 and LC-3) in the acephate-treated rat offspring, thereby suggesting the induction of an autophagic mechanism. Notably, the increased malondialdehyde level, decreased glutathione level, and decreased superoxide dismutase and catalase activities confirmed the ability of acephate to induce oxidative stress and apoptosis in the kidneys of the rat offspring. This may explain the renal histopathological injury detected using hematoxylin and eosin staining. Furthermore, a reverse transcription polymerase chain reaction revealed that the mRNA expression levels of the Na+/K+-ATPase and the epithelial sodium channel (ENaC) genes were significantly higher in the kidney of female offspring than that of controls owing to acephate toxicity. However, there was no significant effect of acephate on the expression of NHE3 in the treatment group compared with the control group. Overall, the present findings suggest that oxidative stress caused by prenatal exposure to acephate causes nephrotoxicity and histopathological alterations in adult rat offspring, likely by actions on renal ENaC and Na+/K+-ATPase genes as well as the autophagic markers Beclin-1 and LC-3.

Hormesis effects in tomato plant growth and photosynthesis due to acephate exposure based on physiology and transcriptomic analysis.

BACKGROUND: Hormesis is a common phenomenon in toxicology described as low-dose stimulation due to a toxin which causes inhibition at a high dose. Pesticide hormesis in plants has attracted considerable research interest in recent years; however, the specific mechanism has not yet been clarified. Acephate is an organophosphorus insecticide that is used worldwide. Here, hormesis in tomato (Solanum lycopersicum L.) plant growth and photosynthesis after acephate exposure is confirmed, as stimulation occurred at low stress levels, whereas inhibition occurred after exposure to high concentrations. RESULTS: We found that low acephate concentration (5-fold lower than recommended application dosage) could enhance chlorophyll biosynthesis and stimulate photosynthesis effects, and thus improve S. lycopersicum growth. A high level of acephate (5-fold higher than recommended application dosage) stress inhibited chlorophyll accumulation, decreased photosystem II efficiency and blocked antioxidant reactions in leaves, increasing reactive oxygen species levels and damaging plant growth. Transcriptomic analysis and quantitative real-time PCR results revealed that the photosynthesis - antenna proteins pathway played a crucial role in the hormesis effect, and that LHCB7 as well as LHCP from the pathway were the most sensitive to acephate hormesis. CONCLUSION: Our results showed that acephate could induce hormesis in tomato plant growth and photosynthesis, and that photosystem II and the photosynthesis - antenna proteins pathway played important roles in hormesis. These results provide novel insights into the scientific and safe application of chemical pesticides, and new guidance for investigation into utilizing pesticide hormesis in agriculture. © 2023 Society of Chemical Industry.

Development of fluorescent aptasensor for detection of acephate by utilizing graphene oxide platform.

A fluorescent graphene oxide based aptasensing platform was developed for the detection of acephate. The aptamers specific to the acephate were screened through GO-SELEX (Graphene Oxide - Systematic Evolution of Ligands by EXponential enrichment) method for six rounds. The screened aptamers were analyzed for their binding affinity and specificity by using fluorescence-based assay. The aptamer AAPT3 that demonstrated highest affinity (Kd = 9 ± 1 nM) and an excellent selectivity, was employed in the development of fluorescent aptasensor. Under optimal conditions, the aptasensor showed low limit of detection (4 ng mL-1) and a wide dynamic linear range (5-80 ng mL-1). The aptasensor was also validated against water samples spiked with acephate, which showed fluorescence recovery from 94 to 107% and coefficient of variation 1-5%. These results indicate that the developed aptasensor can be used for sensitive, selective, and accurate detection of acephate in various samples.

Hazard Assessment of the Effects of Acute and Chronic Exposure to Permethrin, Copper Hydroxide, Acephate, and Validamycin Nanopesticides on the Physiology of Drosophila: Novel Insights into the Cellular Internalization and Biological Effects.

New insights into the interactions between nanopesticides and edible plants are required in order to elucidate their impacts on human health and agriculture. Nanopesticides include formulations consisting of organic/inorganic nanoparticles. Drosophila melanogaster has become a powerful model in genetic research thanks to its genetic similarity to mammals. This project mainly aimed to generate new evidence for the toxic/genotoxic properties of different nanopesticides (a nanoemulsion (permethrin nanopesticides, 20 ± 5 nm), an inorganic nanoparticle as an active ingredient (copper(II) hydroxide [Cu(OH)2] nanopesticides, 15 ± 6 nm), a polymer-based nanopesticide (acephate nanopesticides, 55 ± 25 nm), and an inorganic nanoparticle associated with an organic active ingredient (validamycin nanopesticides, 1177 ± 220 nm)) and their microparticulate forms (i.e., permethrin, copper(II) sulfate pentahydrate (CuSO4·5H2O), acephate, and validamycin) widely used against agricultural pests, while also showing the merits of using Drosophila-a non-target in vivo eukaryotic model organism-in nanogenotoxicology studies. Significant biological effects were noted at the highest doses of permethrin (0.06 and 0.1 mM), permethrin nanopesticides (1 and 2.5 mM), CuSO4·5H2O (1 and 5 mM), acephate and acephate nanopesticides (1 and 5 mM, respectively), and validamycin and validamycin nanopesticides (1 and 2.5 mM, respectively). The results demonstrating the toxic/genotoxic potential of these nanopesticides through their impact on cellular internalization and gene expression represent significant contributions to future nanogenotoxicology studies.

Enantioseparation and dissipation of acephate and its highly toxic metabolite methamidophos in pakchoi by supercritical fluid chromatography tandem mass spectrometry.

Acephate is widely used in crops as racemate. However, the enantioselective dissipation of acephate enantiomers has not been investigated in pakchoi. A sensitive and effective approach was established for determining residues of acephate and its highly toxic metabolite methamidophos enantiomers by supercritical fluid chromatography tandem mass spectrometry. Baseline separations for their enantiomers were achieved by using a Chiralcel OD-H column. The optimal chromatographic conditions were obtained as follows: CO2 /ethanol (95/5) as mobile phase; flow rate, 3.0 mL/min; column temperature, 40°C. The mean recoveries (RSDs) of analytes were in the range of 77-83.1% (6.1-9.9%), 75.4-87.5% (9.3-13.2%), and 81.5-84.2% (7.1-13.4%) at three fortification levels (0.005, 0.05, and 0.5 mg/kg for each enantiomer) for interday assay (n = 18). The method was used to evaluate the enantioselective dissipation of acephate and methamidophos in pakchoi. S-acephate dissipated faster than R-acephate, while the concentration of R-methamidophos was higher than that of S-methamidophos during the entire study period. The results indicated that the R-enantiomer of acephate and methamidophos was preferentially enriched in pakchoi. The established analysis approach and the study data provided useful information for the rational use of acephate in agriculture.

An efficient multi-enzyme cascade platform based on mesoporous metal-organic frameworks for the detection of organophosphorus and glucose.

An efficient colorimetric detection platform based on multi-enzyme cascade has been developed for detection of organophosphorus. Firstly, the dual-enzyme platform was prepared and applied for sensitive glucose detection (detection limit 0.32 µM). And then three enzymes, including acetylcholinesterase, horseradish peroxidase and choline oxidase were encapsulated in cruciate flower-like zeolitic imidazolate framework-8 (CF-ZIF-8) through one-step co-precipitation to construct detection platform with acetylcholine chloride as substrate. The acephate inhibited the activity of acetylcholinesterase, obstructed the cascade reaction and reduced the production of H2O2, resulting in the changes of color intensity for the colorimetric detection. With suitable size and porous structure, CF-ZIF-8 provided a good microenvironment for guaranteeing the activity and spatial proximity of enzymes. The multi-enzyme platform displayed great performances with the detection limit of 0.23 nM for acephate. It was applied to the detection of acephate in Chinese cabbage and romaine, verifying the practicability of this platform.

Novel pathway of acephate degradation by the microbial consortium ZQ01 and its potential for environmental bioremediation.

The microbial degradation of acephate in pure cultures has been thoroughly explored, but synergistic metabolism at the community level has rarely been investigated. Here, we report a novel microbial consortium, ZQ01, capable of effectively degrading acephate and its toxic product methamidophos, which can use acephate as a source of carbon, phosphorus and nitrogen. The degradation conditions with consortium ZQ01 were optimized using response surface methodology at a temperature of 34.1 °C, a pH of 8.9, and an inoculum size of 2.4 × 108 CFU·mL-1, with 89.5% of 200 mg L-1 acephate degradation observed within 32 h. According to the main products methamidophos, acetamide and acetic acid, a novel degradation pathway for acephate was proposed to include hydrolysis and oxidation as the main pathways of acephate degradation. Moreover, the bioaugmentation of acephate-contaminated soils with consortium ZQ01 significantly enhanced the removal rate of acephate. The results of the present work demonstrate the potential of microbial consortium ZQ01 to degrade acephate in water and soil environments, with a different and complementary acephate degradation pathway.

Examination of acephate absorption, transport, and accumulation in maize after root irrigation for Spodoptera frugiperda control.

Since the invasion of the fall armyworm moth (Spodoptera frugiperda) in China in January 2019, damage to maize crops has gradually intensified, and chemical control has become the main control measure. This study aimed to examine methods of effective pest control while monitoring the environmental impact of pesticide use. The effectiveness of S. frugiperda pest control by foliar spraying and root irrigation of maize plants with acephate was determined, and the absorption, distribution, and dissipation of acephate and methamidophos by maize were studied. Field trials showed that acephate treatment at 6000 g a.i. ha-1 was the most effective for controlling S. frugiperda. Acephate and methamidophos were absorbed from the roots, transported upward, and concentrated in the leaves, particularly new leaves. The terminal residues of acephate and methamidophos in maize grains were below detectable levels at 60 days after treatment. The results demonstrate that acephate treatment via root irrigation can more effectively control the infestation of S. frugiperda in maize than acephate treatment via foliar spraying. The translocation and distribution of acephate and methamidophos by root irrigation were more uniform, and the holding efficiency was higher than those in foliar spraying, suggesting an extended period of control efficacy. This pest control method could be utilized to reduce pesticide residues while safely and efficiently controlling S. frugiperda infestation.

Improving the specificity of organophosphorus hydrolase to acephate by mutagenesis at its binding site: a computational study.

Organophosphorus hydrolase (OPH) is one of the most important enzymes in order to bioremediation of organophosphorus (OP) pesticides. OPH is capable of degrading a wide variety of OPs, but it has poor specificity to OPs with P-S bond, including acephate. Given that the binding site residues of OPH determine its substrate specificity, this study was carried out to find the best OPH mutants containing a single point mutation in the binding site that possess improved specificity to acephate. Hence, we generated all possible mutant models and performed molecular docking of acephate with wild-type OPH (OPH-WT) and its mutants. After that, molecular dynamic (MD) simulations of OPH-WT and the best mutants, according to the docking results, were performed in both apo- and complex with acephate forms. Docking results signified that 51 out of 228 mutants possessed increased binding affinities to acephate, as compared to OPH-WT. Of them, W131N, W131G, and H254Y were the best mutants considering the high binding affinities and proper orientation of the ligand at their active sites. MD simulations confirmed the stability of the three mutants in both apo- and complex with acephate forms and also showed that these formed more stable complexes with acephate, as compared to OPH-WT. MD results also suggested that W131N and W131G, in addition to enhanced specificity, could keep the necessary configuration for acephate hydrolysis during the simulations.

Reproductive toxicity in male juvenile rats: Antagonistic effects between isolated agrochemicals and in binary or ternary combinations.

The management of agrochemicals in Brazilian agriculture impacts global environmental sustainability and food security, since this country is one of the major agro-food exporters in the world. Acephate, carbendazim, and dithiocarbamates (DTCs) such as mancozeb, are among the most detected agrochemicals in Brazilian agro-food products, occurring in combination in several crops, especially in fruit cultures. The present study evaluated the impact of the exposure to isolated agrochemicals and all the combined possible mixtures (binary and ternary forms) on the reproductive parameters of male juvenile rats, known to be a vulnerable biological system and developmental window. Data were analyzed using Generalized Linear Models (GzLM), considering each agrochemical as an independent factor. The study revealed higher reproductive toxicity exerted by isolated agrochemicals when compared to the combined treatments, which exhibited mostly an antagonistic effect. Results suggest endocrine disruptive effects of each one separately on the weight of reproductive organs and testicular histomorphometry, besides changes in testicular SOD activity. The full factorial experimental design employed here allowed us to conclude that it is not possible to scale-up the effects of the isolated treatments to the mixtures, showing how difficult it is to know beforehand the response and cross-talk among the multiple physiological mechanisms disturbed by complex mixtures. Considering that food products are shared on a global scale and that some of these three agrochemicals have already been prohibited in EU countries, the consumption of some Brazilian products puts global human health at risk, that of children.

Biodegradation of acephate by Bacillus paramycoides NDZ and its degradation pathway.

Acephate is widely used in agriculture, but its poisonous metabolites and poor sorption characteristics make it a serious environmental pollutant and toxicant to human health. To screen novel bacteria for biodegradation of acephate and uncover its degradation pathway, a strain called NDZ that is capable of utilizing acephate as a sole carbon and energy source was isolated from severely contaminated cultivated land. The bacterium was identified as Bacillus paramycoides based on 16S rDNA sequence analyses. The growth and degradation capacities of B. paramycoides NDZ under different conditions were studied using optical density at 600 nm (OD600) and high-performance liquid chromatography (HPLC). The results showed that B. paramycoides NDZ can grow well with acephate as its sole carbon source (OD600 = 0.76), and degraded about 76% of acephate in mineral salt medium with an initial concentration of 500 mg/L within 48 h. The results of response surface methodology revealed the optimal conditions for degradation was 36 ℃ and pH 6.85 with 526 mg/L acephate. Gas chromatography-mass spectrometry showed that methamidophos was the main metabolite of B. paramycoides NDZ, different from the degradation products of high-temperature steam (121 °C, 103 kPa). Based on the detection of this intermediate, we inferred that acephate was degraded to methamidophos through hydrolysis of the amide linkage, after which methamidophos was degraded to some small molecules, which can be metabolized easily by the bacterium. In summary, B. paramycoides NDZ is a potentially useful bacterium for acephate degradation and remediation of contaminated soils.

Kinetic Study of the Biodegradation of Acephate by Indigenous Soil Bacterial Isolates in the Presence of Humic Acid and Metal Ions.

Many bacteria have the potential to use specific pesticides as a source of carbon, phosphorous, nitrogen and sulphur. Acephate degradation by microbes is considered to be a safe and effective method. The overall aim of the present study was to identify acephate biodegrading microorganisms and to investigate the degradation rates of acephate under the stress of humic acid and most common metal ions Fe(III) and copper Cu(II). Pseudomonas azotoformanss strain ACP1, Pseudomonas aeruginosa strain ACP2, and Pseudomonas putida ACP3 were isolated from acephate contaminated soils. Acephate of concentration 100 ppm was incubated with separate strain inoculums and periodic samples were drawn for UV-visible, FTIR (Fourier-transform infrared spectroscopy) and MS (Mass Spectrometry) analysis. Methamidophos, S-methyl O-hydrogen phosphorothioamidate, phosphenothioic S-acid, and phosphenamide were the major metabolites formed during the degradation of acephate. The rate of degradation was applied using pseudo-first-order kinetics to calculate the half-life (t1/2) values, which were 14.33-16.72 d-1 (strain(s) + acephate), 18.81-21.50 d-1 (strain(s) + acephate + Cu(II)), 20.06 -23.15 d-1 (strain(s) + acephate + Fe(II)), and 15.05-17.70 d-1 (strains + acephate + HA). The biodegradation efficiency of the three bacterial strains can be ordered as P. aeruginosa > P. putida > P. azotoformans. The present study illustrated the decomposition mechanism of acephate under different conditions, and the same may be applied to the removal of other xenobiotic compounds.