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    Effect of Gramoxone Herbicide on Spore Viability and Larvicidal activity of Bacillus sphaericus 2362 and 1593 strains
    (Fresenius Environmental Bulletin, 2003) Berber, İsmet; Atalan, Ekrem; Çökmüş, Cumhur
    Spore viability and larvacidal activity of B. sphaeri-cus 2362 and 1593 strains were monitored in media con-taining Gramaxone® herbicide. Minimal Inhibitory Con-centrations (MICs) of the herbicide were determined for each of the mosquito pathogenic strains. Addition of paraquat into the media suppressed the spore germination after 24 and 48 h, but no influence was observed on parasporal inclusions containing insecticidal toxin pro-teins. SDS-PAGE analysis confirmed the presence of the so-called binary toxin comprising two proteins that are deposited in parasporal crystals treated with the herbicide. Moreover, the number of heat-resistant spores and total cell numbers of test strains were reduced drastically when test strains were grown in media containing 50, 100 and 200 mg ml-1 of paraquat. In contrast, there were no differ-ences between heat-resistant spore counts of both strains when grown under diet concentrations of less than 50 mg ml-1. This study revealed that B. sphaericus 2362 strain has a higher mosquito larvacidal activity than 1593 strain in the presence of paraquat in the media. Thus, the use of Gramaxone® herbicide can have harmful effects on mos-quitocidal biological control agents.
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    Effects of Some Pesticides on Spore Germination and Larvicidal Activity of Bacillus thuringiensis var. israelensis and Bacillus sphaericus 2362 Strain
    (Turkish Journal of Biology, 2004) Berber, İsmet; Çökmüş, Cumhur; Atalan, Ekrem
    The effects of 9 commercial pesticides used commonly in agriculture on spore germination and larvicidal activity of the mosquito pathogenic B. thuringiensis var. israelensis and B. sphaericus 2362 strain were examined. Six of the pesticides was had an inverse impact on spore germination and growth of the test strains. It was determined that the pesticides with the most adverse effect were copper sulfate, methiocarb, and dalapon on spore germination of the microorganisms. Higher concentrations or MIC values of the pesticides reduced the heat-resistant spore numbers of both bioinsecticides, suppressing spore germination. These results indicated that the spores of the bacteria are sensitive to chemical pesticides at the same level. Moreover, the study revealed that the spore germination and larvicidal activity of both biological control agents are affected by pesticides equally. The findings should be considered for assessing the effects of pesticides when both microbial agents are used in field applications.
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    The Influence of Pesticides on the Spore Viability, Toxin Stability and Larvicidal Activity of Bacillus sphaericus 2362 Strain
    (Fresenius Environmental Bulletin, 2004) Berber, İsmet; Atalan, Ekrem; Çökmüş, Cumhur
    In this study, 12 different commercial pesticides, in-cluding 5 fungicides, 5 herbicides, 1 aphicide and 1 acari-cide, were investigated for their effects on spore viability, toxin stability and larvicidal activity of a mosquito patho-genic B. sphaericus 2362 strain. Minimal inhibitory con-centrations (MICs) of each pesticide were determined after 48 h incubation of B. sphaericus 2362 strain. Ac-cording to MIC results, all pesticides showed various inhibitory effects on the growth of the test bacterium. Particularly, the pesticides which contain TCA, hymexa-zol, copper sulphate, hexythiazox, 2,4-D Amine, copper inhibited spore germination significantly and bacterial growth even at the lowest tested concentrations. Our re-sults indicated that various commercial pesticides in dif-ferent concentrations reduced the spore viability signifi-cantly and heat-resistant spore numbers of B. sphaericus 2362 strain. In general, the pesticides decreased the spore numbers 104-105-fold compared to initial ones. Further-more, it was observed that the larvicidal activity was completely lost when it was grown at the concentration of MIC values or higher. Indeed, SDS-PAGE analysis con-firmed that the binary toxin proteins, 41.9 kDa and 51.4 kDa, were lost at the MIC values and higher concentra-tions although parasporal crystals did not disappear in the much lower pesticide concentration.