• Korean journal of applied entomology
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• v.58 no.2
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• pp.101-109
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• 2019

An entomopathogenic bacterium, Xenorhabdus ehlersii KSY, is symbiotic to a nematode, Steinernema longicaudum, and exhibits high entomopathogenic virulence against lepidopteran insects. This study showed that the bacterial pathogenicity is induced by its inhibitory activity against eicosanoid biosynthesis of target insects, resulting in immunosuppression. To be applied for insect pest control, the bacteria should be infected to insect hemocoel. To deliver X. ehlersii to inset hemocoel, Bacillus thuringiensis (Bt) was mixed with the bacteria to breakdown the physical barrier (= midgut epithelium) from midgut lumen to hemocoel. The bacterial mixture significantly enhanced insecticidal activity of Bt only against larvae of Plutella xylostella and Maruca vitrata. For formulation, X. ehlersii cells were freeze-dried and mixed with sporulated Bt cells. The formulated bacterial mixture was applied to semi-field cultivating cabbage crop infested by P. xylostella. The bacterial mixture treatment showed over 95% control efficacy, while Bt alone gave 80% control efficacy. These results suggest that X. ehlersii can be applied to develop a novel insect control agent.

• Journal of Sericultural and Entomological Science
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• v.37 no.1
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• pp.68-73
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• 1995

The toxic effect of Bacillus thuringiensis var, kurstaki $\delta$-endotoxin was determined in the midgut, fat body and Malpighian lobules from larvae of Hyphantria cunea using the au-toradiography and Western blot methods. Bt $\delta$-endotoxin crystals inhibited protein synthesis and elongation factor-2 activity of all tissues tested.

• Food Science and Biotechnology
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• v.15 no.4
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• pp.625-630
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• 2006

Polymerase chain reaction (PCR) method was developed for the specific detection of insect-resistant rice containing cry1Ac gene derived from Bacillus thuringiensis (Bt). Primers were designed from the 35S promoter, NOS terminator, cry1Ac gene, and sucrose phosphate synthase (SPS) for general screening of Bt rice. By sequencing the PCR products from the two putative kinds of Bt rice, we designed a specific primer from the junction region between the cry1Ac gene and the NOS terminator that had been inserted into Bt rice. The construct-specific primer was employed to amplify a 147 bp product in the two lines of Bt rice. No amplified products were observed from the other Bt crops with various Bt genes introduced. In qualitative PCR analysis, the limit of detection was 0.005 ng from genomic DNA of Bt rice. In addition, PCR analysis was performed on 64 kinds of rice presently available in the Korean market, and no Bt rice was detected. This method presented in this paper can be used as a highly sensitive and specific detection method of Bt rice.

• Applied Biological Chemistry
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• v.35 no.4
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• pp.227-231
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• 1992

The plasmids pSUPBT and pSUPBTR were constructed with a vector pSUP2021 and the BT toxin gene in the plasmid pES 1. The plasmids constructed were introduced into the antagonistic rhizobacteria P. fluorescens KR164 by conjugation and P. fluorescens having pSUPBT and pSUPBTR were named P. fluorescens KR164(pSUPBT)#2, KR164(pSUPBT)#3, KR164(pSUPBTR)#2 and KR164(pSUPBTR)#3, respectively. The BT toxin gene were identified in all transformants by Southern hybridization and the final product of BT toxin gene was identified only in P. fluorescens KR164(pSUPBTR)#3 by SDS-PAGE. This crystal toxin protein were also observed in electron microscopy.

• The Korean Journal of Pesticide Science
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• v.16 no.4
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• pp.387-390
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• 2012

Beet armyworm (Spodoptera exigua), diamondback moth (Plutella xylostella) and tobacco cutworm (S. litura) are insect pests causing damage in many economically important vegetables in Korea. Bacillus thuringiensis, commonly known as Bt, has been available as an alternative insecticide for many years. Five commercial Bt products and the mixtures evaluate the control efficacy against three kinds of moths. These commercial Bt products had high control efficacy against $2^{nd}$ instar of diamondback moth, but didn't show high mortality against beet armyworm and tobacco cutworm. Mixtures of Bt products didn't have synergistic effects to the tested moths. Also application of twice and four times the recommended concentration didn't improve the control effects against the tested three species of moths.

• The Korean Journal of Pesticide Science
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• v.18 no.3
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• pp.181-190
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• 2014

An entomopathogenic bacterium, Bacillus thuringiensis (Bt), can sporulate along with production of insecticidal Cry toxins. Bt Cry toxins exhibit relatively narrow spectrum to target insects due to their specific interactions with midgut receptors. This study designed several strategies to enhance Bt efficacy in target insect spectrum and insecticidal activity. Four Cry toxins were purified from four different Bt strains and showed relatively narrow target insect spectrum. However, the Cry mixtures significantly expanded their target insect spectra. The additional effect of baculovirus to Cry toxin was tested with recombinant baculoviruses expressing Cry1Ac or Cry1Ca. However, the baculovirus was little effective to expand target insect spectrum. Bacterial culture broth of Xenorhabdus nematophila (Xn) significantly suppressed insect cellular immune response and increased Cry toxicity. The addition of Xn culture broth to Cry mixture significantly enhanced Bt efficacy in target insect spectrum and insecticidal activity.

• Korean journal of applied entomology
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• v.33 no.3
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• pp.178-183
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• 1994

The prolein components of each crystal toxin of Bacillus thuringiensis kurstaki and alzawai were separated by SDS-PAGE. The major clqistal proteins from both shins were composed of paiypeptides having molecular weights of 130 kd and 64 kd. Digestive mixture of both. toxins with t~ypsin and gut juices shared 62 kd polypeptide which may be major actwe toxh. However, aizawal produced much less amount of 62 kd polypeptide than kurstaki did. On ingestion with Bt &-endotoxin, larvae of Hyphantria cunea developed 45 kd stress protein in the several tissues including fat body, which was induced by heat and cold shock.

• Journal of Microbiology and Biotechnology
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• v.17 no.4
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• pp.547-559
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• 2007

Bacillus thuringiensis (Bt) was first described by Berliner [10] when he isolated a Bacillus species from the Mediterranean flour moth, Anagasta kuehniella, and named it after the province Thuringia in Germany where the infected moth was found. Although this was the first description under the name B. thuringiensis, it was not the first isolation. In 1901, a Japanese biologist, Ishiwata Shigetane, discovered a previously undescribed bacterium as the causative agent of a disease afflicting silkworms. Bt was originally considered a risk for silkworm rearing but it has become the heart of microbial insect control. The earliest commercial production began in France in 1938, under the name Sporeine [72]. A resurgence of interest in Bt has been attributed to Edward Steinhaus [105], who obtained a culture in 1942 and attracted attention to the potential of Bt through his subsequent studies. In 1956, T. Angus [3] demonstrated that the crystalline protein inclusions formed in the course of sporulation were responsible for the insecticidal action of Bt. By the early 1980's, Gonzalez et al. [48] revealed that the genes coding for crystal proteins were localized on transmissible plasmids, using a plasmid curing technique, and Schnepf and Whiteley [103] first cloned and characterized the genes coding for crystal proteins that had toxicity to larvae of the tobacco hornworm, from plasmid DNA of Bt subsp. kurstaki HD-1. This first cloning was followed quickly by the cloning of many other cry genes and eventually led to the development of Bt transgenic plants. In the 1980s, several scientists successively demonstrated that plants can be genetically engineered, and finally, Bt cotton reached the market in 1996 [104].

• Journal of Applied Biological Chemistry
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• v.54 no.4
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• pp.296-302
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• 2011

Insect-resistant transgenic rice was developed by inserting the mCry1Ac1 a modified gene from the soil bacterium Bacillus thuringiensis (Bt). For biosafety assessment, we studied the effects on survival of cantor Daphnia magna, a commonly used as a model organism in ecotoxicological studies. D. magna fed on Bt rice and its near non-genetically modified (GM) counterparts (Nakdong) grown in the same environment (100% ground rice suspension). The Bt rice was comfirmed to have the insertion of T-DNA and protein expression by the polymerase chain reaction and ELISA analysis. Feeding study showed similar cumulative immobility and abnormal response of D. magna between Bt rice and non-GM counterparts. 48 h-$EC_{50}$ values of Bt rice and non-GM rice showed 4,429 and 2,889 mg/L respectively. The rice no observed effect concentration (NOEC) values for D. magna was suggested 1,000 mg/L. We conclude that the tested Bt-rice and Nakdong similar cumulative immobility for D. magna the widely used model organism. We found out that there is strong possibility that the growth of Bt rice didn't affect to non-target insects.

• Applied Biological Chemistry
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• v.35 no.5
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• pp.361-366
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• 1992

The antagonistic bacteria, showing distinguished effect against Fusarium oxysporum and Rhizoctonia solani were isolated from the rhizosphares of horticultural plants and identified as Bacillus subtilis. The strains were studied for their chracteristics of biochemistry, physiology, antagonistic effect against plant pathogenic fungi, and growth promoting effect on horticultural plants. The Bacillus thuringiensis(BT) HD-1 toxin gene was introduced into these B. subtilis. The BT toxin genes on chromosome of the bacteria were identified by southern blotting, but its proteins were not detected by SDS-PAGE. These transformed bacteria showed growth promoting effect and showed also insecticidal and antagonistic effects against Bombix mori and fungi F. oxysporum and R. solani but not against nematode Bursaphelenchus xylophilus.