Dechlorination of Pesticides by a Specific Bacterial Glutathione S‐transferase,BphKLB400: Potential for Bioremediation

The bphK gene located in the bph operon of Burkholderia xenovorans LB400 encodes a protein, BphK^LB400, with significant sequence similarity to glutathione‐S‐transferases (GSTs). GSTs are a superfamily of enzymes involved in the detoxification of many endobiotic and xenobiotic substances. Recently, BphK^LB400 was shown to catalyze the dechlorination of a number of toxic chlorinated organic compounds. Comparison of the amino acid sequence of BphK^LB400 with GSTs from other bacteria that degrade polychlorinated biphenyls identified a number of highly conserved amino acids in the C‐terminal region of the protein thought to be associated with substrate specificity. Mutating the conserved amino acid at position 180 of BphK^LB400 from an alanine to a proline residue resulted in an increase in GST activity of bacterial cell extracts towards a number of chlorinated organic substrates tested including commonly used pesticides. Laboratory scale plant protection experiments suggested that E. coli expressing BphK^LB400 [wildtype and mutant (Ala180Pro)] could protect pea plants from the effects of chloromequat chloride. Therefore, BphK^LB400, identified as having dechlorination activity towards toxic chlorinated organic compounds used in the environment, could have potential in bioremediation.     

Non-omnia moriantur—toxicity of mancozeb on dead wood microarthropod fauna

The effect of Dithane M-45 (dithiocarbamate fungicide; active substance: mancozeb) was studied on microarthropod fauna inhabiting dead wood. Although the exposure was almost never 100% lethal for the majority of observed taxa, almost all (Mesostigmata, Oribatida, some Uropodina, Actinedida, Collembola and Diplopoda) showed very high correlation between concentration of the fungicide and mortality (r > 0.86). Only Stigmaeidae showed low correlation (r = 0.293). For the majority of taxa LC₅₀ values were close to the concentrations used during agrochemical activities in woods. Only Trachytes aegrota showed full susceptibility to the fungicide within the range of recommended field concentrations used in forestry (characterised by the low LC₉₅ value). Tolerance of mesostigmatid and oribatid mites was found to differ between juveniles and adults, but not consistently. Related Uropodina species varied in susceptibility to the fungicide.     

A thermostable phosphotriesterase from the archaeon Sulfolobus solfataricus: cloning, overexpression and properties

A new gene from the hyperthermophilic archaeon Sulfolobus solfataricus MT4, coding for a putative protein reported to show sequence identity with the phosphotriesterase-related protein family (PHP), was cloned by means of the polymerase chain reaction from the S. solfataricus genomic DNA. In order to analyse the biochemical properties of the protein an overexpression system in Escherichia coli was established. The recombinant protein, expressed in soluble form at 5 mg/l of E. coli culture, was purified to homogeneity and characterized. In contrast with its mesophilic E. coli counterpart that was devoid of any tested activity, the S. solfataricus enzyme was demonstrated to have a low paraoxonase activity. This activity was dependent from metal cations with Co²⁺, Mg²⁺ and Ni²⁺ being the most effective and was thermophilic and thermostable. The enzyme was inactivated with EDTA and o-phenantroline. A reported inhibitor for Pseudomonas putida phosphotriesterase (PTE) had no effect on the S. solfataricus paraoxonase. The importance of a stable paraoxonase for detoxification of chemical warfare agents and agricultural pesticides will be discussed.     

The fungicides Terrazole and Terraclor and the nematicide Fenamiphos have little effect on root colonisation by Glomus mosseae and growth of cotton seedlings

 The effect of three pesticides on the initiation and early development of arbuscular mycorrhiza in cotton was examined in experiments under controlled conditions. The fungicides Terrazole and Terraclor initially inhibited mycorrhizal infection of roots of cotton. The inhibition disappeared after 4 weeks, and neither fungicide had a lasting effect. The nematicide Fenamiphos slightly increased shoot dry weight at 6–10 weeks from planting and had no effect on mycorrhizal infection. We conclude that these pesticides have no sustained, detrimental effect on mycorrhizal infection or growth of cotton seedlings when applied at recommended rates. Accepted: 30 May 1997     

A Case Study in Hierarchical Modeling: Agriculture and Prostate Cancer in Iowa

Epidemiologists who study cancer etiology are often asked to conduct etiologic investigations of environmental agents and cancer in populations. The difficulty in estimating the effects of relevant exposures arises because environmental data are usually available only on an aggregate level, such as by county. Individual exposures to chemical agents are usually unknown, as is the joint distribution between the environmental exposure level and disease status. Frequently, some information on the cancer cases themselves is available from a disease registry which typically includes age at diagnosis, gender, and race, and these factors may require control in the analysis. An appropriate statistical model which incorporates this nested data structure is needed. This paper illustrates application of a special case of mixed model, namely hierarchical model, to the study of agricultural factors and prostate cancer in Iowa.     

Alternaria metabolites in sunflower seeds

The alternariol and alternariol monomethyl ether contamination in sunflower seeds was determined. The levels of alternariol found ranged between 35 to 792 µg/kg and 90 to 630 µg/kg for alternariol monomethyl ether. The fungicides showed different effect on the mycotoxin production depending on the substrate, strains and toxin analysed. Mercury phenyl acetate, Octave, Metiram, Thiram and Orthene inhibited alternariol monomethyl ether production while for alternariol production only Thiram, Metiram and Octave were effective.     

Progress in enzyme inhibition based detection of pesticides

The previous few decades have seen the development of biosensors and their use in monitoring of pesticides in food and environmental samples. Although inhibition‐based biosensors have been subject of several recent research works, their performance characteristics greatly depend on the type of immobilization and the presence of interfering compounds in the samples. Moreover, sensitivity, detection limits, and rapidity of the response are few of the other major features that need to be investigated further if they are to become operationally user‐friendly. This review will highlight research carried out in the past on biosensors that are based on enzyme inhibition for determination of organophosphorus compounds and carbamate pesticides.     

Toxic effects of some insecticides,herbicides, and plant essential oils against Tribolium confusum Jacquelin du val (Insecta: Coleoptera: Tenebrionidae)

Cereals are staple food for many countries and are grown on millions of hectares of land, but much of the harvest is wasted due to losses by pests. To minimize these losses, many pesticides are used which are damaging to the environment and human health. There are debates to get rid of these chemicals but they are still in use at large scale. An alternative control strategy for insect pests in storage houses is the use of botanicals. In this study, four plant essential oils, two plant extracts, two herbicides, and two insecticides were used against Tribolium confusum and the comparison of toxicity was made by calculating LC₅₀ and LT₅₀ values. LC₅₀ values were higher for abamectin (2.09–10.23 mg/L) and cypermethrin (3.41–11.78 mg/L) insecticides followed by neem essential oil (7.39–19.24 mg/L) and citrus extract (10.14–24.50 mg/L). However, LC₅₀ values were maximum in case of jaman plant extract (22.38–176.42 mg/L) followed by two herbicides, Logran (19.66–39.72 mg/L) and Topik (29.09–47.67 mg/L) However, LC₅₀ values were higher for topic herbicide (24.098 ppm) and jaman essential oil (16.383 ppm) after four days of treatment. Abamectin and cypermethrin insecticides, neem essential oil and citrus plant extract also killed adults of T. confusum quicker as compared other essential oils, extracts and herbicides. Results revealed that botanical formulations being environmentally safe could be used instead of highly hazardous pesticides for stored products’ pests. This study also elaborates the non-host toxicity of herbicides commonly applied in our agroecosystem.     

农药对生防菌厚孢普可尼亚菌ZK7生长发育的影响

以PDA平板和PDB摇瓶培养法测定了6种常用化学农药对烟草根结线虫生防菌厚孢普可尼亚菌ZK7菌株孢子萌发率、平板抑制作用和液体培养生物量的影响。结果表明,生防菌ZK7菌株对低浓度的6种药剂均存在一定抗性,对不同药剂的抗性表现出差异。其中多菌灵和甲基托布津对生防菌ZK7菌株的抑制作用最大,其次是辛硫磷和雷多米尔,克百威和涕灭威抑制作用最小。