Malathion biodegradation by a psychrotolerant bacteria Ochrobactrum sp. M1D and metabolic pathway analysis

An organophosphorus pesticide malathion biodegradation was investigated by using the bacteria Ochrobactrum sp. M1D isolated from a soil sample of peach orchards in Palampur, District Kangra, Himachal Pradesh (India). The bacterium was able to utilize malathion as the sole source of carbon and energy. The isolated bacterium was found psychrotolerant and could degrade 100% of 100 mg l⁻¹ malathion in minimal salt medium at 20°C, pH 7·0 within 12 days with no major significant metabolites left at the end of the study. Through GCMS analysis, methyl phosphate, diethyl maleate, and diethyl 2-mercaptosuccinate were detected and identified as the major pathway metabolites. Based on the GCMS profile, three probable degradation pathways were interpreted. The present study is the first report of malathion biodegradation at both the psychrophilic and mesophilic conditions by any psychrotolerant strain and also through multiple degradation pathways. In the future, the strain can be explored to bio-remediate the malathion contaminated soil in the cold climatic region and to utilize the enzymatic systems for advanced biotechnology applications.     

Observations on the susceptibility of Ctenocephalides felis (Siphonaptera: Pulicidae) to malathion and permethrin in Tanzania

Laboratory-reared Ctenocephalides felis (Bouche) adults were tested with 0.5% malathion and 0.5% permethrin, using the standard WHO methods. After 24 h exposure to malathion (3.6 mg/cm2), 92% of the fleas died. The LT50 for malathion was approximately 8 h. Permethrin (0.45 mg/cm2) produced 100% mortality of exposed insects after 24 h while with a higher dose (0.9 mg/cm2) all fleas died after 8 h exposure. LT50 for the two doses of permethrin were 7.7 and 1.05 h, respectively. The failure of the diagnostic dose of malathion to kill 100% of the population was attributed to resistance. Permethrin is a suitable pesticide for controlling fleas of domestic animals in Tanzania.     

Melatonin protects against defects induced by malathion during porcine oocyte maturation

Malathion (MAL) is a common organophosphorus pesticide and affects both animal and human reproduction. However, the mechanisms regarding how MAL affects the mammalian oocyte quality and how to prevent it have not been fully investigated. In this study, we used porcine oocyte as a model and proved that MAL impaired porcine oocyte quality in a dose-dependent manner during maturation. MAL decreased the first polar body extrusion, disrupted spindle assembly and chromosome alignment, impaired cortical granules (CGs) distribution, and increased reactive oxygen species (ROS) level in oocytes. RNA-seq analysis showed that MAL exposure altered the expression of 2,917 genes in the porcine maturated oocytes and most genes were related to ROS, the lipid droplet process, and the energy supplement. Nevertheless, these defects could be remarkably ameliorated by adding melatonin (MLT) into the oocyte maturation medium. MLT increased oocyte maturation rate and decreased the abnormities of spindle assembly, CGs distribution and ROS accumulation in MAL-exposed porcine oocytes. More important, MLT upregulated the expression of genes related to lipid droplet metabolism (PPARγ and PLIN2), decreased lipid droplet size and lipid peroxidation in MAL-exposed porcine oocytes. Finally, we found that MLT increased the blastocysts formation and the cell numbers of blastocysts in MAL-exposed porcine oocytes after parthenogenetic activation, which was mediated by reduction of ROS levels and maintaining lipid droplet metabolism. Taken together, our results revealed that MLT had a protective action against MAL-induced deterioration of porcine oocyte quality.     

Toxicological and biochemical characterizations of malathion sensitivity in two field populations of Oxya chinensis （Orthoptera： Acridoidea）

We evaluate comparative toxicity of malathion in the two populations of the grasshopper Oxya chinensis, collected from Daixian and Fanshi of Shanxi province, China. General esterases and acetylcholinesterase （ACHE） from the two populations were characterized and compared. LD50 of the Daixian population （7.58 μg/g body weight） was 2.02-fold higher than that of the Fanshi population （3.75μg/g body weight）. General esterase-specific activities in the Daixian population were 1.91,130 and 1.85-fold higher than those in the Fanshi population, when α-NA, α-NB and β-NA were used as a substrate, respectively. Kinetic studies of general esterase showed that Vmax values of general esterases hydrolyzing α-NA,α-NB and β-NA in the Daixian population were 2.15-, 1.12-, and 1.47-fold, respectively, higher than those in the Fanshi population. The AChE activity of the Fanshi population was 1.54-fold higher than that of the Daixian population. Kinetic analysis of AChE showed that significant differences were presented between the two populations in the Km values; and the Vmax value in the Fanshi population was higher than that in the Daixian population. Inhibition studies of AChE indicated that AChE from the Daixian population was 2.56-, 2.80-, and 2.29-fold less sensitive to inhibition by paraoxon, chlorpyrifos-oxon, and demeton-S-methyl, respectively, than that from the Fanshi population. These biochemical characterizations of general esterases and AChE were consistent with malathion bioassay in the two populations. It is inferred that the reduced sensitivity of altered AChE and increased general esterase activities play an important role in the differences of insusceptibility of Oxya chinensis to malathion between the two populations.     

Biodegradation of Malathion with Indigenous Acclimated Activated Sludge in Batch Mode and in Continuous-Flow Packed-Bed Reactor

Acclimated activated sludge was examined for its ability to degrade malathion with and without the presence of glucose as a potential cometabolite substrate. In this study, a packed-bed reactor (PBR) using three kinds of biofilm carriers was employed for efficient degradation of malathion. The results obtained indicate that microorganisms tested were able to degrade malathion. The observed degradation rate of the pesticide in the presence of glucose was the same as without glucose. The activated sludge was found to be able to use malathion as the sole phosphorus source. In contrast, the degradation ability of the activated sludge was lost when the pesticide was used as the sole source of sulfur. The degradation capacity of the PBR was higher than the performance obtained with the batch reactor. The reactor packed with crushed olive kernels exhibited the best performance, allowing a total removal of malathion (10 mg/dm³) within 12 h.     

褐飞虱对马拉硫磷的抗性遗传和交互抗性研究

毒力测定显示,抗马拉硫磷品对杀螟松、二嗪磷、异丙威和仲丁威都有明显的交互抗性产生,但对醚菊酯和吡虫啉没有表现出显的交互抗性。抗性遗传研究显示,正交和反交后代F1和F1'的显性值D分别为0.4014和0.3780,说明抗性主效基因是不完全显性的。通过自交后代F2和回交后代BC的LD-p线观察及与期望曲线比较,证明抗性遗传由两个或两个以上的基因控制。     

羧酸酯酶和乙酰胆碱酯酶在褐飞虱对马拉硫磷抗性发展中的作用

对室内筛选褐飞虱Nilaparvata lugens Stal对马拉硫磷抗性及羧酸酯酶、乙酰胆碱酯酶的连续变化进行了研究。结果表明,抗性发展在不同世代之间存在一定的变化。LD₅₀的最大变化发生在第3代和第5代之间。在筛选的前5代,羧酸酯酶活性上升与马拉硫磷抗性变化存在很好的相关性,而乙酰胆碱酯酶敏感性在第6代和第8代间的变化与抗性发展存在很好的相关性。可见,羧酸酯酶活性的上升在抗性发展的早期阶段起重要作用,而乙酰胆碱酯酶不敏感在抗性发展的后期阶段起更重要作用。     

Insecticide resistance enhances male reproductive success in a beetle

Abstract.— Malathion-specific resistance in the red flour beetle, Tribolium castaneum , is widespread and stable in natural populations even in the absence of pesticide exposure. To understand this stability, both resistant and susceptible males were placed in competition for susceptible female fertilization. Females were then isolated and their progeny was tested for malathion susceptibility. Male reproductive success was estimated for populations originating from different geographic areas and for isogenic strains. In most cases, resistant males had a greater reproductive success rate than susceptibles. The results suggest that male reproductive success is not traded against the selection for malathion resistance, even resistant individuals are at an advantage for this fitness trait. This absence of fitness cost may be the result of postselection of (1) modifier gene which ameliorate the fitness of resistant individuals or (2) nondeleterious resistance gene. Resistant phenotype superiority could be due to increased male mating success, improved ability of resistant males in sperm competition, female mate choice, and/or cryptic female choice of resistance gene(s). The effect of male phenotypic frequency on male reproductive success was also examined. We observed that male fertilization success is frequency dependent and inversely related to their frequency. However, this "rare male" advantage did not counteract the superiority of the resistant males.     

Medfly eradication in California:

The impact of malathion-bait sprays (directed against medfly, Ceratitis capitata [Wiedemann]) on an endemic gall midge (Rhopalomyia californica Felt) and its parasitoids was investigated during 1982–83 in the south San Francisco Bay area of northern California. In a heavily sprayed area (Woodside), a population explosion of the midge was detected following 24 applications of malathion bait. The midge population reached levels ca. 90x greater than those observed in an adjacent unsprayed area (Jasper Ridge). In a moderately sprayed area (Portola Valley), the midge population increased as much as 5x that observed in the adjacent unsprayed area (Jasper Ridge), following 12 applications of malathion bait. In laboratory tests, the malathion bait was toxic to both the midge and its parasitoids. The major parasitoids were Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica (Ashmead) and Mesopolobus sp. Population increases of the midge following malathion-bait sprays were attributed to destruction of parasitoids and other natural enemies of the midge. If the environmental impact of malathion-bait sprays is related to the number of applications (as suggested in this study), then it would be worthwhile to determine the appropriate bait-spray strategy for a given situation, so as to minimize adverse effects on nontarget species, yet insure suppression or eradication of medfly.

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Résumé L'impact des pièges tratiés au malathion (destinés à Ceratitis capitata Wiedem) sur Rhopalomyia californica Felt et ses parasitoïdes a été examiné en 1982–1983 dans le sud de la zone de la baie de San Francisco en Californie. Dans une zone fortement traitée (Woodside), une explosion de population a été décelée après 24 traitements. La population de R. californica a atteint des niveaux 90 fois supérieurs à ceux observés dans une zone contiguë non traitée (Jasper Ridge). Dans une zone modérément traitée (Portola Valley), avec 12 traitement, la population de R. californica a atteint jusqu'a 5 fois celle de Jasper Ridge. Au laboratoire, le piège à malathion a été toxique tant pour R. californica que pour ses parasitoïdes, dont les principaux étaient: Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica(Ashmead) et Mesopolobus sp. L'accroissement de la population de C. capitata après traitement a été attribué à la destruction de parasitoïdes et d'autres ennemis naturels. Si l'effet su l'environnement du traitement est lié au nombre d'interventions (comme le suggère cette étude), alors cela vaudrait la peine de définir une stratégie de traitement appropriée à une situation donnée, de façon à minimiser les effets négatifs sur des espèces non visées, tout en assurant la suppression ou l'éradication de C. capitata.

     

Cost-comparison of DDT and alternative insecticides for malaria control

In anti-malaria operations the use of DDT for indoor residual spraying has declined substantially over the past 30years, but this insecticide is still considered valuable for malaria control, mainly because of its low cost relative to alternative insecticides. Despite the development of resistance to DDT in some populations of malaria vector Anopheles mosquitoes (Diptera: Culicidae), DDT remains generally effective when used for house-spraying against most species of Anopheles, due to excitorepellency as well as insecticidal effects. A 1990 cost comparison by the World Health Organization (WHO) found DDT to be considerably less expensive than other insecticides, which cost 2 to 23 times more on the basis of cost per house per 6 months of control. To determine whether such a cost advantage still prevails for DDT, this paper compares recent price quotes from manufacturers and WHO suppliers for DDT and appropriate formulations of nine other insecticides (two carbamates, two organophosphates and five pyrethroids) commonly used for residual house-spraying in malaria control programmes. Based on these 'global' price quotes, detailed calculations show that DDT is still the least expensive insecticide on a cost per house basis, although the price appears to be rising as DDT production declines. At the same time, the prices of pyrethroids are declining, making some only slightly more expensive than DDT at low application dosages. Other costs, including operations (labour), transportation and human safety may also increase the price advantages of DDT and some pyrethroids vs. organophosphates and carbamates, although possible environmental impacts from DDT remain a concern. However, a global cost comparison may not realistically reflect local costs or effective application dosages at the country level. Recent data on insecticide prices paid by the health ministries of individual countries showed that prices of particular insecticides can vary substantially in the open market. Therefore, the most cost-effective insecticide in any given country or region must be determined on a case-by-case basis. Regional coordination of procurement of public health insecticides could improve access to affordable products.