• BMB Reports
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• v.46 no.3
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• pp.175-180
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• 2013

Cyt2Aa2 is a mosquito larvicidal and cytolytic toxin produced by Bacillus thuringiensis subsp. darmstadiensis. The toxin becomes inactive when isoleucine at position 150 was replaced by alanine. To investigate the functional role of this position, Ile150 was substituted with Leu, Phe, Glu and Lys. All mutant proteins were produced at high level, solubilized in carbonate buffer and yielded protease activated product similar to those of the wild type. Intrinsic fluorescence spectra analysis suggested that these mutants retain similar folding to the wild type. However, mosquito larvicidal and hemolytic activities dramatically decreased for the I150K and were completely abolished for I150A and I150F mutants. Membrane binding and oligomerization assays demonstrated that only I150E and I150L could bind and form oligomers on lipid membrane similar to that of the wild type. Our results suggest that amino acid at position 150 plays an important role during membrane binding and oligomerization of Cyt2Aa2 toxin.

• BMB Reports
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• v.34 no.2
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• pp.130-133
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• 2001

The amino acid sequences of 130 kDa and 72 kDa proteins responsible for the larvicidal activity of Bacillus thuringiensis var israelensis (Bti) were analyzed by hydrophobic moment plots. A search for highly amphiphilic $\alpha$-helices was made in these proteins using the helical hydrophobic moment as a criterion of amphiphilicity The protein segments of the largest hydrophobic moments were analyzed. In the present communication we report the surface seeking helices in 130 kDa and 72 kDa proteins of Bacillus thuringiensis var israelensis. It is assumed that the surface seeking segments may participate in one of the membrane-related functions of Bacillus thuringiensis.

• Microbiology and Biotechnology Letters
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• v.23 no.4
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• pp.390-396
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• 1995

Bacillus sphaericus 1593 is a larvicidal toxin-producing mosquitocidal bacterium. The toxin contains a parasporal crystalline inclusion which is composed of a protein that is activated under alkaline condition. To enhance alkaline environment around toxin protein, cryptic plasmid cured, B. sphaericus 1593 was transformed by the Bacillus pasteurii urease gene which generate ammonia from urea. Transformant produced urease at about 80% more than wild type strain. B. sphaericus 1593, and the urease gene was stably maintained. It also produced crystalline toxin protein at the same level as the wild type strain B. sphaericus 1593.

• The Korean Journal of Pesticide Science
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• v.6 no.4
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• pp.257-263
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• 2002

This study was carried out not only to investigate the toxicities of 12 registered insecticides on different developmental stages, but also to determine the sublethal effects on longevity and reproduction of newly emerged adult female and development of the next generation in the rice skipper, Parnara guttata. Fenitrothion, fenthion, cartap hydrochloride, ethofenprox highly suppressed egg-hatch. All insecticides treated showed high larvicidal activity on the 1st to 2nd instar larva. The insecticides showed higher larvicidal activities on the 5th instar larva were fenitrothion, fenthion, ethofenprox, fipronil, methoxyfenozide, tebufenozide and Bt. var. kurstaki. The sublethal doses of fenthion, tebufenozide, cartap hydrochloride, methoxyfenozide, ethofenprox, imidacloprid and fipronil shortened the longevities of newly emerged adult female from the treated larva ($3{\sim}4$ instar). BPMC, imidacloprid, ethofenprox, fipronil and methoxyfenozide delayed the preoviposition periods of adult females and decreased the number of eggs laid when they were treated at the larval stages of the previous generation. Ethofenprox caused severe sublethal effects on P. guttata offspring, completely blocking the production. All insecticides except fenitrothion affected the egg viability, and all eggs from the adult females emerged from the survivors treated larvae with imidacloprid or fipronil fail to hatch. IGRs, methoxyfenozide and tebufenozide showed an adverse effect on the development of next generation larva.

• Korean journal of applied entomology
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• v.43 no.2
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• pp.169-173
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• 2004

Control effects of some insecticides were evaluated against the stone leek leafminer, Liriomyra chinensis Kato (Diptera： Agromyzidae) with the some different treatment methods. Insecticidal activities effects were estimated on the different development stages of the insects on welsh onion. The insecticides that controlled L. chinensis eggs with over 83％ efficacy were spinosad, dimethoate, emamectin, and cartap. The insecticides that showed over 87％ of larvicidal activity were dimethoate and cartap. Dimethoate showed 93.3％ insecticide residual activity for 3 days a(ter treatment as a foliar spray. For control of pupae, the insecticides that showed over 88％ of contact insecticidal activity were terbufos GR and cartap GR. Both dimethoate and cartap had high adulticidal activity with over 95％ control efficacy.

• Microbiology and Biotechnology Letters
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• v.23 no.2
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• pp.156-163
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• 1995

Bacillus sphaericus 1593 is pathogenic to the larvae of a number of mosquito species that are known as important vectors for the transmission of certain human and animal diseases. As a preliminary experiment for developing a multfunctional B. sphaericus 1593 as a potent antagonist, we investigated the conditions for the protoplast transformation system of B. sphaericus 1593 using the plasmid pGB215-110$\Delta$B. The protoplast of B. sphaericus 1593 were obtained most efficiency by treating the cells with 500 $\mu$g/ml of lysozyme in the SMM buffer containing 0.5 M sucrose at pH 8.0 and 40$\circ$C for 60 minutes. The cell wall was regenerated on the plate containing 1.2% agar and 0.8 M mannitol. Under the best condition for protoplast formation and regeneration established in the work the highest frequency of transformation was achieved with the 40% PEG (M.W 4,000) treatment for 15 minutes of incubation at 4$\circ$C, and subsequently for 120 minutes incubation at 30$\circ$C for phenotypic expression. The highest transformation efficiency were observed at 1.0 $\mu$g/ml of the final concentration of the plasmid DNA and the plasmids were found to be fairly stable since about 70% of the plasmids were maintained after 8 successive daily transfers onto the fresh medium.

• BMB Reports
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• v.43 no.1
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• pp.23-28
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• 2010

Binary toxin consisting of BinA and BinB from Bacillus sphaericus is toxic to mosquito larvae. BinB is responsible for specific binding to the larval gut cell membrane while BinA is crucial for toxicity. To investigate functional role of cysteine in BinB, three cysteine residues at positions 67, 161, and 241 were replaced by alanine or serine. Mutations at these positions did not affect protein production and overall structure of BinB. These cysteine residues are not involved in disulfide bond formation between BinB molecules. Mosquito-larvicidal assays revealed that C67 and C161 are essential for toxicity, whereas C241 is not. Mutations at C67 and C161 resulted in weaker BinA-BinB interaction. The loss of toxicity may be due to the reduction of interactions between BinA and BinB or BinB and its receptor. C67 and C161 could also play a part during conformational changes or internalization of the binary toxin into the target cell.

• The Korean Journal of Pesticide Science
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• v.3 no.1
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• pp.46-50
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• 1999

Methanol extracts of 9 kinds of native medicinal plants(Taraxacum platycarpum, leaf; Pinus densiflora, leaf; Artemisia prinseps, leaf; Allium tuberosum, leaf; Cassia obtussifolia, whole; Sophora angestifolia, root; Stemonae sessilifolia, root; Lonicera japonica stem, leaf, flower; and Clivia miniata) were investigated for insecticidal effect. Methanol extracts of Pinus densiflora leaves and Sophora angestifolia radix showed relatively good insecticidal activity against Culex pipiens pallens larvae. Strong larvicidal activity against the Musca domestica larvae was produced from methanol extracts of Taraxacum platycarpum leaves and Allium tuberosom leaves. while Stemonae radix showed moderate activity. All materials tested revealed little or weak insecticidal activity against M. domestica adults.

• Korean journal of applied entomology
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• v.31 no.4
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• pp.475-479
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• 1992

The non-steroidal ecdysone agonist RH 5849 showed almost similar LC.o values( 18.1-26.5 ppm) at all stages of larval development of the tobacco cutworm, Spodoptera litura, when treated by a leaf-disk dipping method. The feeding-inhibition rate for the 4th instar larvae was dose-dependent, and simultaneously the weight gain of 3rd instar larvae ceased within 48 hour after feeding of the cabbage leafdisk dipped into RH 5849 4.2 ppm solution. The systemic larvicidal effect of RH 5849 was compared at cabbage and tobacco whole plant test. The $LC_{50}$ values below 20 ppm(mg/kg soil) was lasted for 15 days in cabbage, 30 days in tobacco respectively.

• BMB Reports
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• v.36 no.3
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• pp.294-298
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• 2003

The pathological effect of the Bacillus thuringiensis Cry $\delta$-endotoxins on susceptible insect larvae had extensive damage on the midgut epithelial cells. In this study, an ex vivo assay was devised for assessing the insecticidal potency of the cloned Cry4B mosquito-larvicidal protein that is expressed in Escherichia coli. Determination of toxicity was carried out by using a cell viability assay on the midguts that were dissected from 5-day old Aedes aegypti mosquito larvae. After incubation with the toxin proteins, the number of viable epithelial cells was determined photometrically by monitoring the quantity of the bioreduced formazan product at 490 nm. The results showed that the 65-kDa trypsin-activated Cry4B toxin exhibited toxic potency ca. 3.5 times higher than the 130-kDa Cry4B protoxin. However, the trypsin-treated products of the non-bioactive Cry4B mutant (R158A) and the lepidopteran-specific Cry1Aa toxin displayed relatively no ex vivo activity on the mosquito-larval midguts. The ex vivo cytotoxicity studies presented here confirms data that was obtained in bioassays.