Evaluation of esterases hydrolyzing α-naphthyl acetate as markers for malathion resistance in Culex quinquefasciatus.

Early detection of insecticide resistance is essential to develop resistance countermeasures and depends on accurate and rapid biological and biochemical tests to monitor resistance and detect associated mechanisms. Many such studies have measured activities of esterases, enzymes associated with resistance to ester- containing insecticides, using the model substrate, α-naphthyl acetate (α-NA). However, in the field, pests are exposed to ester-containing insecticides such as malathion, that are structurally distinct from α-NA. In the current study, malathion resistance in C. quinquefasciatus (3.2- to 10.4-fold) was highly associated with esterase activity measured with either α-NA (R2 = 0.92) or malathion (R2 = 0.90). In addition, genes encoding two esterases (i.e., EST-2 and EST-3) were over-expressed in field- collected strains, but only one (EST-3) was correlated with malathion hydrolysis (R2 = 0.94) and resistance (Rs = 0.96). These results suggest that, in the strains studied, α-NA is a valid surrogate for measuring malathion hydrolysis, and that heightened expression of an esterase gene is not necessarily associated with metabolic resistance to insecticidal esters.

Superior oxidase-mimetic activity of FeCo-NC dual-atom nanozyme for smartphone-based visually colorimetric assay of organophosphorus pesticides.

A colorimetric analysis platform has been successfully developed based on FeCo-NC dual-atom nanozyme (FeCo-NC DAzyme) for the detection of organophosphorus pesticides (OPPs). The FeCo-NC DAzyme exhibited exceptional oxidase-like activity (OXD), enabling the catalysis of colorless TMB to form blue oxidized TMB (oxTMB) without the need for H2O2 involvement. By combining acid phosphatase (ACP) hydrolase with FeCo-NC DAzyme, a "FeCo-NC DAzyme + TMB + ACP + SAP" colorimetric system was constructed, which facilitated the rapid detection of malathion. The chromogenic system was applied to detect malathion using a smartphone-based app and an auxiliary imaging interferogram device for colorimetric measurements, which have a linear range of 0.05-4.0 µM and a limit of detection (LOD) as low as 15 nM in real samples, comparable to UV-Vis and HPLC-DAD detection methods. Overall, these findings present a novel approach for convenient, rapid, and on-site monitoring of OPPs.

The effect of enterosgel on the activity of energy supply processes in rats at the same time affected by malathion and tetrachlormethane.

OBJECTIVE: Aim: The aim of the study was to investigate the activity of bioenergetic processes in rats under conditions of simultaneous exposure to malathion and carbon tetrachloride and after the use of enterosgel. PATIENTS AND METHODS: Materials and Methods: Experiments were conducted on rats. The rats were divided into nine groups.Malathion was administered daily (for 30 days) at a dose of 20 mg / kg body weight of the animal. Tetrachloromethane was administered twice (every other day) as a 50% oil solution at a dose of 1.0 ml / kg body weight. The intensity of energy supply processes was assessed by the activity of succinate dehydrogenase and cytochrome oxidase, impaired carbohydrate metabolism in terms of glucose and glycogen. RESULTS: Results: It was noted that succinate dehydrogenase activity in the liver decreased 2 times, in the myocardium - 1.6 times. On the thirty and seventh day of administration of toxicants after enterosorbent use, succinate dehydrogenase activity increased in the liver by 20%, cytochrome oxidase by 27%, in the myocardium - by 31% and 23%, respectively. The content of glucose in the serum after exposure to toxicants increased maximally (2.4 times) at the end of the study. In contrast, the glycogen content in the liver decreased by 48%, in the myocardium by 13%. The use of enterosgel resulted in a decrease in serum glucose. CONCLUSION: Conclusions: The use of enterosgel leads to the restoration of energy processes in the body of affected rats, which is confirmed by increased activity of mitochondrial enzymes, lowering glucose and increasing glycogen in the studied organs.

Potential key genes involved in metabolic resistance to malathion in the southern house mosquito, Culex quinquefasciatus, and functional validation of CYP325BC1 and CYP9M12 as candidate genes using RNA interference.

BACKGROUND: Metabolic detoxification is one of the major mechanisms contributing to the development of resistance in mosquitoes, including the southern house mosquito, Culex quinquefasciatus. The three major detoxification supergene families, cytochrome P450s, glutathione S-transferases and general esterases, have been demonstrated to play an important role in metabolic resistance. In this study, we performed differential gene expression analysis based on high-throughput transcriptome sequencing on samples from four experimental groups to give insight into key genes involved in metabolic resistance to malathion in Cx. quinquefasciatus. We conducted a whole transcriptome analysis of field captured wild Cx. quinquefasciatus from Harris County (WI), Texas and a malathion susceptible laboratory-maintained Sebring colony (CO) to investigate metabolic insecticide resistance. Field captured mosquitoes were also phenotypically classified into the malathion resistant and malathion susceptible groups following a mortality response measure conducted using a Centers for Disease Control and Prevention (CDC) bottle assay. The live (MR) and dead (MS) specimens from the bottle assay, along with an unselected WI sample and a CO sample were processed for total RNA extraction and subjected to whole-transcriptome sequencing. RESULTS: We demonstrated that the genes coding for detoxification enzymes, particularly cytochrome P450s, were highly up-regulated in the MR group compared to the MS group with similar up-regulation observed in the WI group compared to the CO group. A total of 1,438 genes were differentially expressed in comparison between MR and MS group, including 614 up-regulated genes and 824 down-regulated genes. Additionally, 1,871 genes were differentially expressed in comparison between WI and CO group, including 1,083 up-regulated genes and 788 down-regulated genes. Further analysis on differentially expressed genes from three major detoxification supergene families in both comparisons resulted in 16 detoxification genes as candidates potentially associated with metabolic resistance to malathion. Knockdown of CYP325BC1 and CYP9M12 using RNA interference on the laboratory-maintained Sebring strain significantly increased the mortality of Cx. quinquefasciatus after exposure to malathion. CONCLUSION: We generated substantial transcriptomic evidence on metabolic detoxification of malathion in Cx. quinquefasciatus. We also validated the functional roles of two candidate P450 genes identified through DGE analysis. Our results are the first to demonstrate that knockdown of CYP325BC1 and CYP9M12 both significantly increased malathion susceptibility in Cx. quinquefasciatus, indicating involvement of these two genes in metabolic resistance to malathion.

Head lice: an inexpensive bioassay for use as guidance for healthcare workers monitoring treatment failures for insecticide resistance (1994-1999).

Head lice, Pediculus humanus capitis De Geer (Psocodea: Pediculidae) that failed to respond to pyrethroid insecticide-based treatment products were first identified in London and Cambridge, UK, in 1993 after which reports of treatment failure arose throughout the UK. There was a need amongst healthcare workers for a rapid detection method for resistance that could be used at the community level. A laboratory service was set up so that health professionals could send lice by overnight post for bioassay testing for resistance. In addition, test kits were provided so that testing could either be conducted on site or lice could be shipped to the laboratory on pre-treated test papers so that insecticide exposure could proceed while lice were in transit to the laboratory. Between 1994 and 1999, over 350 samples from 145 locations were tested and during this time populations of lice resistant to pyrethroids, malathion, and carbaryl were identified from all parts of the country, both urban and rural. In some areas, lice were only resistant to one of the insecticides available but in other places lice showed tolerance to all three insecticides used at the time.

Pesticides residues determination and probabilistic health risk assessment in the soil and cantaloupe by Monte Carlo simulation: A case study in Kashan and Aran-Bidgol, Iran.

Cantaloupe is a popular agricultural product in the hot season of Iran. On the other hand, the frequent use of pesticides in cantaloupe fields is the most important threat to the health of farmers and consumers. Therefore, the present study aims to measure the concentration of diazinon (DZN), chlorpyrifos (CPF), and malathion (MLT) in cantaloupe cultivated in Kashan and Aran-Bidgol (Iran) and to estimate the possible oral and dermal risk of these pesticides by Monte Carlo simulation (MCS). 36 cantaloupe samples, 18 samples before, and 18 samples after the latent period were collected from different places of cantaloupe cultivation from April to May 2021. After measuring the pesticides using the QuEChERS approach, oral and dermal risk assessments were calculated.The mean and standard deviation of the concentrations of chlorpyrifos, malathion, and diazinon in 18 cantaloupe samples, after the latent period, were (30.39 ± 13.85), (18.361 ± 1.8), and (21.97 ± 0.86) µg kg-1, respectively. Concentration of Malathion, diazinon, and Chlorpyrifos in the soil were 0.22, 0.25, and 0.3 mg kg-1, respectively, and pesticide cumulative risk assessment in soil was obtained 0.011 for Malathion, 0.05 for diazinon and 0.03 for Chlorpyrifos. Target Hazard Quotient (THQ) according to the cantaloupe consumption and dermal exposure in children and adults, was safe range. Although non-cancerous dermal and oral risk of cantaloupe is low, constant exposure can be harmful. Therefore, the findings of this study play an important role in increasing the understanding of the negative health consequences of pesticide contamination in cantaloupe for consumers, especially local residents, and can help by adopting remedial strategies to reduce environmental concerns.

Molecular and biochemical investigation of the protective effects of rutin against liver and kidney toxicity caused by malathion administration in a rat model.

Widely used malathion (MLT) causes environmental pollution, leading to toxicity in many living things, including humans. Rutin (RUT) is a flavonoid with various biological properties. In the present study, the protective effects of rutin against liver and kidney toxicity caused by malathion were investigated. In the study, MLT (100 mg/kg) and RUT (50 or 100 mg/kg) were administered to rats alone or in combination for 28 days. Then, oxidative stress, inflammation, endoplasmic reticulum stress (ERS), apoptosis, and autophagy markers in liver and kidney tissues were analyzed by biochemical and molecular methods. The results showed that MLT caused oxidative stress in both tissues, while RUT showed antioxidant properties and protected these tissues from oxidative damage. Moreover, MLT upregulated the expressions of ATF-6, PERK, IRE1, GRP78, and CHOP, leading to ERS. However, RUT alleviated ER stress and suppressed these markers. The study also found that MLT increased inflammatory, apoptotic, and autophagic markers. All these factors affected liver and kidney functions and caused an increase in plasma ALT, AST, urea, and creatinine levels. On the other hand, it has been observed that RUT may protect liver and kidney tissues from the destructive effect of MLT by showing anti-inflammatory, anti-apoptotic, and anti-autophagic properties. Thus, it was determined that ALT, AST, urea, and creatinine levels decreased after RUT treatment. As a result, it was observed that MLT had a toxic effect on the liver and kidney tissues of rats, and it was determined that this toxicity could be alleviated by RUT treatment.

Bimetallic AuPt alloy/rod-like CeO2 nanojunctions with high peroxidase-like activity for colorimetric sensing of organophosphorus pesticides.

Organophosphorus pesticides (OP) have extensive applications in agriculture, while their overuse causes inevitable residues in food, soil, and water, ultimately being harmful to human health and even causing diverse dysfunctions. Herein, a novel colorimetric platform was established for quantitative determination of malathion based on peroxidase mimic AuPt alloy decorated on CeO2 nanorods (CeO2@AuPt NRs). The synthesized nanozyme oxidized colorless 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. Besides, the oxidized TMB was inversely reduced by ascorbic acid (AA), which were originated from hydrolysis of L-ascorbic acid-2-phosphate (AA2P) with the assistance of acid phosphatase (ACP). Based upon this observation ACP analysis was explored by colorimetry, showing a wid linear range of 0.2 ~ 3.5 U L-1 and a low limit of detection (LOD = 0.085 U L-1, S/N = 3). Furthermore, malathion present in the colorimetric system inhibited the activity of ACP and simultaneously affected the generation of AA, in turn promoting the recovery of the chromogenic reaction. Based on this, the LOD was decreased to 1.5 nM (S/N = 3) for the assay of malathion with a wide linear range of 6 ~ 100 nM. This simple colorimetric platform provides some informative guidelines for determination of other pesticides and disease markers.

Hairpin DNA-enabled ratiometric electrochemical aptasensor for detection of malathion.

A hairpin DNA-enabled ratiometric electrochemical aptasensor is reported for sensitive and reliable detection of malathion (MAL). The approach employs hairpin DNA (ferrocene-labeled, Fc-hDNA) as a carrier to hybridize MAL aptamers (methylene blue-labeled, MB-Apt) to form double-stranded DNA structures on an electrode. The presence of MAL induces the removal of aptamers, and hDNA re-forms hairpin structures, causing a decrease in the oxidation current of MB (IMB) and an increase in the oxidation current of Fc (IFc). The ratiometric signal of IFc/IMB responds quantitatively to MAL concentrations. To compare analytical performances, a linear single-stranded DNA (ssDNA) is also used to construct the ssDNA-based aptasensor. We demonstrate that hairpin DNA possessing a rigid two-dimensional structure can improve the assembly efficiency of aptamers and the stability of redox probes. The approach combines the advantages of the ratiometric electrochemical method with hairpin DNA-based conformational switching probes, enabling hDNA-based aptasensor with enhanced sensitivity and reliability, offering a linear range of 0.001 to 1.0 ng mL-1. The platform was applied to detect MAL in lettuce, and the statistical analysis indicated that no significant differences were found between the developed platform and HPLC-MS.

Exposure to Insecticides Modifies Gene Expression and DNA Methylation in Hematopoietic Tissues In Vitro.

The evidence supporting the biological plausibility of the association of permethrin and malathion with hematological cancer is limited and contradictory; thus, further studies are needed. This study aimed to investigate whether in vitro exposure to 0.1 µM permethrin and malathion at 0, 24, 48 and 72 h after cell culture initiation induced changes in the gene expression and DNA methylation in mononuclear cells from bone marrow and peripheral blood (BMMCs, PBMCs). Both pesticides induced several gene expression modifications in both tissues. Through gene ontology analysis, we found that permethrin deregulates ion channels in PBMCs and BMMCs and that malathion alters genes coding proteins with nucleic acid binding capacity, which was also observed in PBMCs exposed to permethrin. Additionally, we found that both insecticides deregulate genes coding proteins with chemotaxis functions, ion channels, and cytokines. Several genes deregulated in this study are potentially associated with cancer onset and development, and some of them have been reported to be deregulated in hematological cancer. We found that permethrin does not induce DNA hypermethylation but can induce hypomethylation, and that malathion generated both types of events. Our results suggest that these pesticides have the potential to modify gene expression through changes in promoter DNA methylation and potentially through other mechanisms that should be investigated.

Network Analysis of Biomarkers Associated with Occupational Exposure to Benzene and Malathion.

Complex diseases are associated with the effects of multiple genes, proteins, and biological pathways. In this context, the tools of Network Medicine are compatible as a platform to systematically explore not only the molecular complexity of a specific disease but may also lead to the identification of disease modules and pathways. Such an approach enables us to gain a better understanding of how environmental chemical exposures affect the function of human cells, providing better perceptions about the mechanisms involved and helping to monitor/prevent exposure and disease to chemicals such as benzene and malathion. We selected differentially expressed genes for exposure to benzene and malathion. The construction of interaction networks was carried out using GeneMANIA and STRING. Topological properties were calculated using MCODE, BiNGO, and CentiScaPe, and a Benzene network composed of 114 genes and 2415 interactions was obtained. After topological analysis, five networks were identified. In these subnets, the most interconnected nodes were identified as: IL-8, KLF6, KLF4, JUN, SERTAD1, and MT1H. In the Malathion network, composed of 67 proteins and 134 interactions, HRAS and STAT3 were the most interconnected nodes. Path analysis, combined with various types of high-throughput data, reflects biological processes more clearly and comprehensively than analyses involving the evaluation of individual genes. We emphasize the central roles played by several important hub genes obtained by exposure to benzene and malathion.

Utilization of the copper recovered from waste printed circuit boards as a metal precursor for the synthesis of TiO2/magnetic-MOF(Cu) nanocomposite: Application in photocatalytic degradation of pesticides in aquatic solutions.

In this study, a number of leaching solutions (H2SO4, CuSO4 and NaCl) and an electrochemical method were used together for the separation of Cu from waste printed circuit boards. Secondly, the magnetic-MOF(Cu) was synthesized using the Cu recovered from waste printed circuit boards. Thereafter, TiO2/mag-MOF(Cu) composite was prepared and its photocatalytic activity was assessed in the photo degradation of two prominent organophosphorus pesticides, namely malathion (MTN) and diazinon (DZN). The catalytic structure of the MOF-based composite was fully characterized by various analyses such as XRD, SEM, EDAX, FT-IR, VSM and UV-vis. The obtained analyses confirmed the successful synthesis of TiO2/mag-MOF(Cu) composite. The synthesized composite exhibited highly efficient in the degradation of both pollutants under the following conditions: pH 7, contaminant concentration 1 mg/L, the catalyst dosage of 0.4 g/L, visible light intensity 75 mW/cm2 and reaction time of 45 min. First order kinetic model was best suited with the experimental results (R2: 0.97-0.99 for different MTN and DZN concentrations). Trapping studies revealed that superoxide radicals (O2•-) played an important role during the degradation process. Furthermore, the catalyst demonstrated a superb recovery as well as high stability over five cyclic runs of reuse. In addition, the total organic carbon (TOC) analysis showed over 83% and 85% mineralization for MTN and DZN, respectively. The combined system of TiO2/mag-MOF(Cu)/Vis also exhibited a great level of efficiency and feasibility in the treatment of tap water and treated wastewater samples. It is concluded that TiO2/mag-MOF(Cu) could be used as an excellent catalyst for the photodegradation of MTN and DZN in aqueous solution.

Vitamin B12 alleviates malathion-induced toxicity in zebra fish by regulating cytochrome P450 and PgP expressions.

The indiscriminate and rampant use of pesticides has raised serious concerns regarding their toxic impact on non-target organisms which underlines need for the development of an effective antidote. Metabolic activation of organophosphate pesticides by the phase I enzyme, cytochrome P450 plays a key role in influencing pesticide-toxicity. In this study, we have investigated the effect of environmentally relevant malathion concentration (100 µg/L) alone and in combination with vitamin B12 on the expression of genes related to xenobiotic metabolism such as CYP enzymes, PgP and the key oxidative stress responsive transcription factor, Nrf2 in zebra fish liver and brain. Expressions of Nrf2-trasncribed antioxidant genes and their activities were also measured. Administration of vitamin B12 successfully revived motor functions by modulation of AchE activity. Mechanistically, vitamin B12 was demonstrated to alleviate oxidative stress which was accompanied by decreased phase-I enzyme cyp3c1 and increased pgp expressions.

Biodegradation of malathion by Micrococcus sp. strain MAGK3: kinetics and degradation fragments.

Malathion is widely used as an agricultural insecticide, but its toxic nature makes it a serious environmental contaminant. To screen indigenous bacteria for malathion degradation, a strain MAGK3 capable of utilizing malathion as its sole carbon and energy source was isolated from Pennisetum glaucum agricultural soil. Based on morphological and biochemical characteristics and 16S rDNA sequence analysis, strain MAGK3 was identified as Micrococcus aloeverae. The strain was cultured in the presence of malathion under aerobic and energy-restricting conditions, and it grew well in MSM containing malathion (1000 µl/L), showing the highest specific growth rate at 500 µl/L. Reverse-phase UHPLC-DAD analysis indicated that 100%, 90.48%, 84.27%, 75.46%, 66.65%, and 31.96% of malathion were degraded within 15 days in liquid culture augmented with 50, 100, 200, 300, 500, and 1000 µl/L concentrations of commercial malathion, respectively. Confirmation of malathion degradation to malathion mono, diacids, and phosphorus moiety was performed by Q-TOF-MS analysis, and a pathway of biodegradation was proposed. The influence of co-substrates was also examined to optimize biodegradation further. Kinetic studies based on different models were conducted, and the results demonstrated good conformity with the first-order model. Malathion degradation process by Micrococcus aloeverae was characterized by R2 of 0.95, and the initial concentration was reduced by 50% i.e. (DT50) in 8.11 d at an initial concentration of 500 µl/L. This establishes the Micrococcus sp. as a potent candidate for active bioremediation of malathion in liquid cultures as it can withstand high malathion load and can possibly impact the development strategies of bioremediation for its elimination.

Peptide nanotube functionalized molecularly imprinted polydopamine based single-use sensor for impedimetric detection of malathion.

In the present study, a peptide nanotube functionalized polydopamine (p-Dop) based molecularly imprinted (MIP) sensor system was constructed, characterized, and studied for the impedimetric sensing of an organophosphorus pesticide, malathion (MLT). Electropolymerization in the presence of a template (MLT) was utilized as a convenient and effective strategy to generate imprinted p-Dop films on peptide nanotubes (PNTs) modified graphite electrodes (PGEs). Upon the removal of template, the adsorption of MLT on the specific cavities formed in the MIP film was tracked using electrochemical impedance spectroscopy (EIS). To attain optimal sensor response, experimental conditions, such as film thickness, analyte/functional monomer ratio, and desorption/adsorption time, were analyzed. The obtained MIP(p-Dop)-PNT-PGE sensor exhibited high sensitivity for electrochemical MLT analysis with a wide dynamic detection range of 13 pg mL-1 - 1.3 µg mL-1 and a LOD of 1.39 pg mL-1. The combination of a bio-inspired p-Dop-based MIP with the EIS technique allowed excellent sensitivity and selectivity toward MLT sensing which also yielded high recoveries in real samples. The success of this research strategy in real samples revealed its potential for various future environmental applications.

Ameliorative effect of selenium yeast supplementation on the physio-pathological impacts of chronic exposure to glyphosate and or malathion in Oreochromis niloticus.

BACKGROUND: Pesticide exposure is thought to be a major contributor to living organism health deterioration, as evidenced by its impact on both cultured fish species and human health. Commercial fish diets are typically deficient in selenium (Se); hence, supplementation may be necessary to meet requirements during stress. Therefore, this study was conducted to investigate the protective role of selenium yeast (SY) supplementation for 60 days against the deleterious effects of glyphosate and or malathion chronic toxicity at sublethal concentrations in Oreochromis niloticus . METHODS: Two hundred and ten fish were divided into seven groups (n = 30/group) as follows: G1 (negative control); G2 (2 mg L- 1 glyphosate); G3 (0.5 mg L- 1 malathion); G4 (glyphosate 1.6 mg L- 1 and malathion 0.3 mg L- 1); G5 (glyphosate 2 mg L- 1 and SY 3.3 mg kg- 1); G6 (malathion 0.5 mg L- 1 and SY 3.3 mg kg- 1); and G7 (glyphosate 1.6 mg L- 1; malathion 0.3 mg L- 1 and SY 3.3 mg kg- 1). RESULTS: Results revealed significant alteration in growth performance parameters including feed intake (FI), body weight (BW), body weight gain (BWG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). G4 has the highest documented cumulative mortalities (40%), followed by G3 (30%). Additionally, the greatest impact was documented in G4, followed by G3 and then G2 as severe anemia with significant thrombocytopenia; leukocytosis; hypoproteinemia; increased Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST), urea, and creatinine, as well as malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Considering the previously mentioned parameters, selenium yeast (Saccharomyces cerevisiae) (3.3 mg kg- 1 available selenium) mitigated the negative impact of both the agrochemicals, whether exposed singly or in combination, in addition to their antioxidative action. CONCLUSIONS: In conclusion, our study found that organophosphorus agrochemicals, single or combined, had negative impacts on Oreochromis niloticus regarding growth performance, biochemical and hematological changes in the serum, as well as induced oxidative damage in liver and kidney tissues. Supplementation of SY at the rate of 3.3 mg kg- 1 diet (2.36 mg kg- 1 selenomethionine and 0.94 mg organic selenium) ameliorated the fish performance and health status adversely affected by organophosphorus agrochemical intoxication.

Fitness cost of malathion resistance in Egyptian Culex pipiens populations.

The extensive use of insecticides in agriculture and public health has resulted in the rapid development of insecticide resistance in mosquito populations. Therefore, in this study, we aimed to evaluate insecticide resistance costs on the fitness of Culex pipiens. Two Cx. pipiens field populations (Beheira malathion-resistant and Gharbia malathion-susceptible) were compared to the reference (sensitive) population. The biochemical composition and expression of four genes relevant to insecticide resistance were estimated in third instar larvae. Adult survival, female fecundity and egg hatchability were also determined. As per our findings, it was found that the total protein and carbohydrate contents in Beheira malathion-resistant larvae were significantly lower than that in the reference larvae. Beheira malathion-resistant larvae had higher phenoloxidase (PO) specific activity than the reference population. In terms of the relevant genes, only cytochrome P450 (CYP6F1) expression showed elevated levels in the Gharbia malathion-susceptible population compared to the Beheira malathion-resistant population. In esterases (Estα and Estß) and glutathione S-transferase, the tested populations did not show any significant differences. Compared to the reference mosquito population, Gharbia malathion-susceptible Cx. pipiens males exhibited significantly longer median survival. Female fecundity and hatchability showed nonsignificant differences among the populations tested. In conclusion, malathion resistance can induce lower protein and carbohydrate contents, but higher PO activity in larvae.

Optimizing the malathion degrading potential of a newly isolated Bacillus sp. AGM5 based on Taguchi design of experiment and elucidation of degradation pathway.

Malathion, a pesticide used to control pests in crops, vegetables, fruits, and livestock. Its widespread and indiscriminate usage has ensued in different ecological issues, thus, it's vital to remediate this insecticide. Malathion degrading bacterium Bacillus sp. AGM5, isolated from pesticide contaminated agricultural field was cultured in presence of different malathion concentrations under aerobic and energy restrictive conditions and was found effective at malathion degradation. Recovered malathion was extracted based on QuEChERS approach and then analyzed by UHPLC. About 39.5% of malathion biodegradation was observed at 300 µlL-1 after 96 h of incubation with the tested bacteria which increased to 58.5% and 72.5% after 240, and 360 h of incubation, respectively. To further enhance malathion biodegradation, the effects of co-substrates, pH, temperature, initial malathion concentration, agitation (rpm), and inoculum size were evaluated using Taguchi methodology. Taguchi DOE's ability to predict the optimal response was established experimentally via optimised levels of these factors (glucose-0.1%, yeast extract-0.1%, inoculum size-2% wv-1, malathion concentration 300 µlL-1, rpm-150, pH-7, temperature 40 °C), whereby biodegradation rate was enhanced to 95.49% after 38 h. Confirmation of malathion biodegradation was performed by UHPLC, Q-TOF-MS, GC-MS analysis and a possible degradation pathway was proposed for malathion biodegradation. First order kinetic model was appropriate to describe malathion biodegradation. The Taguchi DOE proved to be viable tool for optimizing culture conditions and analysing the interactions between process parameters in order to attain the best feasible combination for maximum malathion degradation. These results could influence the development of a bioremediation strategy.

Malathion-resistant Tribolium castaneum has enhanced response to oxidative stress, immunity, and fitness.

Many cases of insecticide resistance in insect pests give resulting no-cost strains that retain the resistance genes even in the absence of the toxic stressor. Malathion (rac-diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]succinate) has been widely used against the red flour beetle, Tribolium castaneum Herbst. in stored products although no longer used. Malathion specific resistance in this pest is long lasting and widely distributed. A malathion resistant strain was challenged with a range of stressors including starvation, hyperoxia, malathion and a pathogen to determine the antioxidant responses and changes to some lifecycle parameters. Adult life span of the malathion-specific resistant strain of T. castaneum was significantly shorter than that of the susceptible. Starvation and/or high oxygen reduced adult life span of both strains. Starving, with and without 100% oxygen, gave longer lifespan for the resistant strain, but for oxygen alone there was a small extension. Under oxygen the proportional survival of the resistant strain to the adult stage was significantly higher, for both larvae and pupae, than the susceptible. The resistant strain when stressed with malathion and oxygen significantly increased catalase activity, but the susceptible did not. The resistant strain stressed with Paranosema whitei infection had significantly higher survival compared to the susceptible, and with low mortality. The malathion resistant strain of T. castaneum showed greater vigour than the susceptible in oxidative stress situations and especially where stressors were combined. The induction of the antioxidant enzyme catalase could have helped the resistant strain to withstand oxidative stresses, including insecticidal and importantly those from pathogens. These adaptations, in the absence of insecticide, seem to support the increased immunity of the insecticide resistant host to pathogens seen in other insect species, such as mosquitoes. By increasing the responses to a range of stressors the resistant strain could be considered as having enhanced fitness, compared to the susceptible.

Evaluations of two glutathione S-transferase epsilon genes for their contributions to metabolism of three selected insecticides in Locusta migratoria.

The insect-specific epsilon class of glutathione S-transferases (GSTEs) plays important roles in insecticide detoxification in insects. In our previous work, five GSTEs were identified in Locusta migratoria, and two recombinant GSTEs, rLmGSTE1 and rLmGSTE4, showed high catalytic activity when 1-chloro-2,4-dinitrobenzene (CDNB) was used as a substrate. In this work, we further investigated whether these two GSTEs could metabolize three insecticides including malathion, deltamethrin and DDT. Using ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC/MS) method, we found that rLmGSTE4, but not rLmGSTE1, can metabolize malathion and DDT. Malathion bioassays of L.migratoria after the expression of LmGSTE4 was suppressed by RNA interference (RNAi) showed increased insect mortality from 33.8% to 68.9%. However, no changes in mortality were observed in deltamethrin- or DDT-treated L.migratoria after the expression of LmGSTE4 was suppressed by RNAi. Our results provided direct evidences that LmGSTE4 participates in malathion detoxification in L.migratoria. These findings are important for understanding the mechanisms of insecticide resistance in L.migratoria and developing new strategies for managing the insect populations in the field.