Plasmid-associated biodegradation of an organophosphorus pesticide, Monocrotophos, by Pseudomonas mendocina

Pseudomonas mendocina isolated from soil degraded an insecticide, Monocrotophos (MCP), by 67% and harbored a 7.4 kb plasmid, designated as pMCP424. On the basis of curing and transformation experiments, MCP degradation by Pseudomonas mendocinawas plasmid-borne and transferable to other bacteria.     

有机磷农药对土壤动物毒性的影响研究

有机磷农药对土壤动物毒性影响的试验结果表明,土壤动物对农药毒性反应敏感,4种有机磷农药处理组的动物种类和数量明显减少,动物种类的减少主要是常见种和稀有种类,动物数量变化则主要是优势类群的数量消长,毒性毒理试验表明,农药对大型土壤动物蚯蚓有明显致死效应,并对蚯蚓,鞘翅目幼虫和等足类鼠妇虫等大型动物的呼吸强度有显著抑制作用,其呼吸代谢强度随着农药处理浓度增加与染毒历时的延长而迅速减弱。     

Biomineralization of carbonate and phosphate by moderately halophilic bacteria

We investigated the precipitation of carbonate and phosphate minerals by 19 species of moderately halophilic bacteria using media with variable Mg(2+)/Ca(2+) ratios. The precipitated minerals were calcite, magnesium (Mg) calcite, and struvite (MgNH(4)PO(4) x 6H(2)O) in variable proportions depending on the Mg(2+)/Ca(2+) ratio of the medium. The Mg content of the Mg-calcite decreased with increasing Ca(2+) concentration in the medium. According to the saturation indices, other minerals could also have precipitated. We observed important differences between the morphology of carbonate and phosphate, which may help us to recognize these minerals in natural systems. We studied the growth and pH curves of four bacteria in media specific for carbonate and struvite precipitation. We consider the biomineralization processes that produce carbonate and phosphate minerals, and propose a hypothesis for the lack of struvite in natural environments and ancient rocks.     

Diversity of organophosphorus pesticide-degrading bacteria in a polluted soil and conservation of their organophosphorus hydrolase genes

Seven methyl parathion-degrading bacteria were isolated from a long-term methyl parathion contaminated soil and were found to belong to the genera Pseudaminobacter, Achromobacter, Brucella, and Ochrobactrum. Southern blot analysis using an mpd gene probe revealed that their hydrolase genes were similar to the mpd gene from Plesiomonas sp. strain M6 and were all located on the chromosome. Gene libraries were constructed from genomic DNA of each of the 7 organophosphorus pesticide-degrading bacteria, and their mpd genes were cloned and sequenced. Sequence analysis revealed that their hydrolase genes were conserved, and that the G+C content of the mpd genes were distinctly different from that of the chromosome-located 16S rRNA gene, suggesting that the mpd gene could be transferred and expressed among a variety of bacterial hosts.     

Effect of two organophosphorus insecticides on the phosphate-dissolving soil bacteria.

Dimethoate and malathion added to soil at 10 and 100 microgram/g caused an initial stimulation of CO2 production. Total counts of bacterial propagules were increased. All insecticide applications increased bacteria producing phospholipases from week 1 until week 4 after the application; bacteria then returned to the original levels.     

有机磷农药中毒救治初探

目的 探讨有机磷农药中毒(AOPP)的抢救方法.方法 对大连市金州区第三人民医院1995年9月至2011年9月共收治20例有机磷农药中毒患者的病例进行回顾性分析.结果 18例治愈,2例转到上级医院治疗.平均住院8.5d.结论 抢救有机磷农药中毒,洗胃是关键措施之一.快速达到阿托品化是抢救有机磷农药中毒成功与否的另一关键性措施.     

Reactivation of immobilized acetyl cholinesterase in an amperometric biosensor for organophosphorus pesticide

Biosensors based on acetyl cholinesterase (AChE) inhibition have been known for monitoring of pesticides in food and water samples. However, strong inhibition of the enzyme is a major drawback in practical application of the biosensor which can be overcome by reactivation of the enzyme for repeated use. In the present study, enzyme reactivation by oximes was explored for this purpose. Two oximes viz., 1,1'-trimethylene bis 4-formylpyridinium bromide dioxime (TMB-4) and pyridine 2-aldoxime methiodide (2-PAM) were compared for the reactivation of the immobilized AChE. TMB-4 was found to be a more efficient reactivator under repeated use, retaining more than 60% of initial activity after 11 reuses, whereas in the case of 2-PAM, the activity retention dropped to less than 50% after only 6 reuses. Investigations also showed that reactivation must be effected within 10 min after each analysis to eliminate the ageing effect, which reduces the efficiency of reactivation.     

构建全细胞生物传感器测定农田土壤中有机磷农药甲基对硫磷含量

土壤中污染物的生物有效性评估对于准确评价环境污染风险至关重要,而全细胞生物传感器是此类评估的重要工具之一。本研究旨在使用新型全细胞生物传感器建立土壤中甲基对硫磷(methyl parathion,MP)的检测方法。首先,使用筛选出的甲基对硫磷水解酶基因(methyl parathion degrading gene,mpd)和pUC19质粒骨架以及已有的特异性诱导元件pobR为材料,构建全细胞生物传感器。然后,以96孔的酶标板为载体和以5种全细胞生物传感器为指示细胞,建立了土壤提取液样品中甲基对硫磷的分析方法,并应用于实际测试和田间土壤样品中甲基对硫磷的检测。以检测性能的最佳大肠杆菌(Escherichia coli)DH5α/pMP-AmilCP为例,其检测限为6.21−6.66μg/L,线性范围为10−10000μg/L。E.coli DH5α/pMP-RFP和E.coli DH5α/pMP-AmilCP的方法用于分析土壤提取液样品中甲基对硫磷的浓度,具有较好的检测性能。这种全细胞生物传感器方法有助于快速评估土壤中甲基对硫磷的生物有效性强弱,从而有效判断有机磷农药甲基对硫磷对土壤的污染风险。     

污染土壤中有机磷农药降解菌的分离及其多样性

采用添加有机磷农药的选择性培养基,在长期受有机磷农药污染的土壤中分离到7株有机磷农药降解菌,经生理生化鉴定和系统发育分析,菌株mp-1鉴定为Pseudaminobactersp.,菌株mp-2为Alcaligenessp.,菌株mp-7为Brucellasp.,其他菌株为Ochrobactrumsp.。16SrDNA序列同源性比较、系统发育分析和染色体ERIC-PCR指纹图谱扩增表明有机磷农药长期污染的土壤中有机磷农药降解菌具有丰富的多样性。     

Whole-body metabolism of the organophosphorus pesticide, fenthion, in goldfish, Carassius auratus

The in vivo metabolism of fenthion, an organophosphorus pesticide, and its sulfoxide (fenthion sulfoxide) was examined in goldfish (Carassius auratus). When goldfish were administered fenthion i.p. at a dose of 100 mg/kg, two metabolites were isolated from the tank water. They were identified as fenthion sulfoxide and fenthion oxon, in which > P = S of fenthion is transformed to > P = O, by comparing their mass and UV spectra, and their behavior in HPLC and TLC, with those of authentic standards. However, fenthion sulfone was not detected as a metabolite. The amounts of fenthion, fenthion sulfoxide and fenthion oxon excreted within 4 days were 2.7, 3.4 and 2.5%, of the initial dose of fenthion, respectively. Unchanged fenthion was detected in the body of the fish to the extent of 42-50% of the dose after 10 days, but fenthion sulfoxide and fenthion oxon showed very low concentrations. When fenthion sulfoxide was administered to the fish, about 70% of the dose was excreted unchanged into the tank water within 24 h, but little of the reduced compound, fenthion, was found. In contrast, fenthion was detected at 2.1% of dose in the body of goldfish as a metabolite of fenthion sulfoxide. The fact that fenthion is metabolized to the toxic oxon form in fish presumably has environmental and health implication for its use as a pesticide.     

Localisation of identical organophosphorus pesticide degrading (opd) genes on genetically dissimilar indigenous plasmids of soil bacteria: PCR amplification,cloning and sequencing of opd gene from Flavobacterium balustinum

Plasmid borne organophosphorus pesticide degrading (opd) gene of Flavobacterium balustinum has been amplified using polymerase chain reaction (PCR) and the resulting PCR product (1.25 Kb) was cloned in pUC18. Further, a detailed restriction map was determined to PCR product and subcloned as overlapping restriction fragments. The nucleotide sequence was determined for all subclones to obtain complete sequence of PCR amplified fragment. The sequence showed 98% similarity to opd genes cloned from other soil bacteria isolated from diversified geographical regions. The protein sequence predicted from the nucleotide sequence was almost identical to parathion hydrolase, a triesterase involved in hydrolysis of triester bond found in variety of op-pesticides. The signal sequence of parathion hydrolase contained recently discovered twin arginine transport (tat) motif. It appears that tat motif plays a critical role in membrane targeting of parathion hydrolase.     

Growth rate influences reductive biodegradation of the organophosphorus pesticide demeton by Corynebacterium glutamicum

The organophosphorous pesticide, demeton-S-methyl was transformed byCorynebacterium glutamicum in co-metabolism with more readilydegradable substrates. Glucose, acetate and fructose were tested as growth substrates, and the highest demeton-S-methyl biotransformation average rate (0.78 mg l^-1 h^-1) and maximum instantaneous rate (1.4 mg l^-1 h^-1) were achieved on fructose. This higher efficiency seems to be linked to the atypical behavior of C. glutamicum grown on fructose, characterized by a prolonged period of accelerating growth instead of a constant growth rate observed on glucose or acetate. More precisely, for growth rates in the 0.1–0.4 h^-1 range, a direct coupling between the specific demeton-S-methyl consumption rate and the growth rate was demonstrated on fructose during batch –, steady state continuous – or continuous cultures with a controlled transient growth rate (accelerostat technology). The demeton-S-methyl biotransformation was more favoured during an acceleration phase of the growth rate.     

Oxidation of ethylene by soil bacteria

The course of the biological oxidation of ethylene by soil was dependent on the type of soil used as well as on other factors. As evidenced from an increase in oxidation rate, the ethylene-consuming microorganisms in soil could grow at the expense of ethylene, even when the gas was present at concentrations of 50 ppm or less. Five strains of bacteria strongly resembling each other were isolated from different soils. These pleomorphic, gram-positive, acid-fast, obligate aerobic, ethylene-oxidizing bacteria grew also on saturated alkanes and on ordinary carbon sources. An apparent K_m for ethylene of approximately 40 ppm was estimated for whole-cell suspensions of strain E20 by following the disappearance of the gas from the atmosphere.     

Toxicity of fenitrothion, an organophosphorus pesticide, against summer population of sunn pest, Eurygaster integriceps Put. (Hemiptera: Scutelleridae)

The sunn pest are a group of insect representing several genera of the shield bug (Scutelleridae) and stink bug (Pentatomidae) families, with the species Eurygaster integriceps being the most economically important. The sunn pest is a major pest of wheat and barley in central and western Asia and it accounts for annual losses of 20-30% for barley and up to 100% for wheat. In the recent decades problems have intensified largely due to change in farming practices. Thus this pest threatens food security and reduces the stability of traditionally wheat-based agricultural systems. In order to control pest, the major organophosphorus insecticide used is fenitrothion. So, the aim of the current study was to determine toxicity of fenitrothion against summer population of adult sunn pest. Insecticide toxicity was measured using a topical bioassay. To do so, the toxin was dissolved in acetone and six concentrations of toxin including 25, 50, 100, 150, 175 and 200 ppm were prepared. Insects were treated on the pronotum with one micro litre aliquots of insecticide in acetone (for treatments) or acetone alone (for control). The dose-mortality relationship was assessed from above mentioned doses with 30 insects treated per dose. After treatment, insects were maintained at laboratory conditions and mortality was recorded after 48 hours. Results were corrected for control mortality with Abbott's formula and then analyzed and toxicity determined. The obtained results showed that LD10, LD50, and LD90 were 34.7, 90.43, and 235.5, respectively.     

Mutagenicity of organophosphorus compounds in bacteria and drosophila

140 Organophosphorus compounds (OP's) have been tested for mutagenic activity in bacteria, principally by using two specially constructed sets of tester strains of the bacteria Salmonella typhimurium and Escherichia coli. It was found that 20% gave positive mutagenic responses and that this group of chemicals produce base substitutions rather than frame-shift mutations. In most cases the DNA repair genes exrA⁺ and recA⁺ were for mutagenic activity.Seven compounds were further tested in Drosophila melanogaster for the ability to induce recessive lethal mutations. In some of these cases the doses administered to the flies had to be very low due to the highly toxic nature of the compounds. To overcome this problem, the accumulation of recessive lethal mutations was measured in populations which were continually exposed to the compounds over a period of some 18 months. During this time the populations developed increased resistance to the compound and so the dose administered could gradually be increased. Six of the compounds were mutagenic.Of the compounds tested in both systems, those showing mutagenic activity in bacteria were also mutaganic in Drosophila, those mutagenic in bacteria were not mutagenic in Drosophila.