• Journal of Microbiology and Biotechnology
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• v.4 no.3
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• pp.171-175
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• 1994

To find new crystal protein genes, we screened 42 Bacillus thuringiensis strains of serovar standards by Southern hybridization with a cryI-specific probe which was amplified from B. thuringiensis subsp. kurstaki HDl by polymerase chain reaction (PCR). Two strains, B. thuringiensis subsp. entomocidus HD9 and subsp. subtoxicus HD109, generated weak signals under the low-stringency hybridization conditions. Further analysis with Southern hybridization revealed that the two strains contained cryIB genes which are slightly different from those of B. thuringiensis subsp. thuringiensis HD2. These results were confirmed by PCR with cryIB-specific primers followed by the restriction analysis of PCR products.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.772-776
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• 2004

Physiological and molecular characteristics of Bacillus thuringiensis SR6 and SR8 were investigated, and phase contrast and electron microscopies revealed that a large rhomboidal crystal protein was present in the sporulating cells. SDS-PAGE and Western blot analyses showed that B. thuringiensis SR8 produced 70 kDa protein much more than other proteins, and that the 70 kDa protein could bind to the antibody of B. thuringiensis subsp. tenebrionis-crystal toxin protein, indicating that the crystal 70 kDa protein has an immunological homology with B. thuringiensis subsp. tenebrionis-crystal toxin protein. The DNA fragment of B. thuringiensis subsp. tenebrionis-toxin gene was detected in B. thuringiensis SR6 and SR8 by using PCR amplification analysis. Furthermore, the insect bioassay showed the insecticidal activity against Colorado potato beetle larvae. Based on the physiological and molecular similarities to B. thuringiensis subsp. tenebrionis, it is suggested that the B. thuringiensis SR6 and SR8 may be mutants of the B. thuringiensis subsp. tenebrionis strain overexpressing the crystal of 70 kDa toxin protein.

• Microbiology and Biotechnology Letters
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• v.21 no.5
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• pp.428-434
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• 1993

Cloning and expression of two different crystal protein genes from transformed Bacillus thuringiensis were investigated. B. thuringiensis NT0423 is toxic to both Lepidopterous and Dipte-rous larvae. The pCG5 vector carrying crystal protein genes (mosquitocidal and hemolytic activity) of B. thurigiensis subsp. morrisoni PG-14 was transformed into B. thurigiensis NT0423. Transformant has expressed two type crystals of bipyramid from NT0423 and ovoid from pCG5 in one cell.

• Microbiology and Biotechnology Letters
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• v.21 no.3
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• pp.193-199
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• 1993

Effects of the five fermenation media on the growth and the production of endotoxin of twenty-five Bacillus thuringiensis isolates were investigated. Among the five different media, the growth and the production of endotoxin of B. thuringiensis were highest in the M4 and M5 media containing high amounts of nitrogen and carbohydrate. But the production of endotoxin was highest in the M1 and M3 media containing high amounts of nitrogen sources limiting carbohydrate. The average number of endotoxin and growth(O.D.) in the M1 and M3 medial were 4.4*107/ml and 2.42 in M1 medium and 1.3*107/ml and 1.46, respectively.

• Microbiology and Biotechnology Letters
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• v.33 no.2
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• pp.154-158
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• 2005

Twenty-three Bacillus thuringiensis strains isolated from Korea were screened to detect the cry-type genes using PCR with 21 specific oligonucleotide primers. Eight strains contained distinct multiple crystal genes; cry1Aa2, cry1Ab1, cry1Ac1 and cry2Aa1. These results indicate that the strains coincided with the B. thuringiensis subsp. kurstaki strain. The other 15 strains were not recognised to the 21 specific primers.

• Korean journal of applied entomology
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• v.34 no.4
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• pp.373-377
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• 1995

Four Bacillus thuringiensis isolates obtained from soil samples in Korea produce parasporal inclusions non-toxic to 10 insect species of three orders, Lepidopera, Diptera and Coleoptera. These four isolates are named NTB-1, NTB-2, NTB-3 and NTB-4, respectively. The morphology of parasporal inclusions of four isolates observed by phase contrast- and scanning electron microscope was all ovoid. Characterization of four non-toxic B. thuringiensis isolates was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and restriction endonuclease analysis. The results showed that parasporal inclusion proteins and total plasmid DNA profiles of four isolates are different from other known non-toxic B. thuringiensis strains', suggesting that four isolates are novel.

• Microbiology and Biotechnology Letters
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• v.35 no.3
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• pp.250-254
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• 2007

Bacillus thringiensis strain 108 was isolated from soil and had nematicidal activity against second stage juvenile of plant root-knot nematode, Meloidogyne incognita. The strain 108, a rod shape, spore forming and Gram positive bacterium, produced lecithinase, catalase, and ${\delta}$-endotoxin. The strain 108 belongs to H serotype 3, Bacillus thuringiensis var. kurstaki. A nematicidal substance of the strain 108 was partially purified on Sephadex G-25 gel filtration, activated carbon adsorption, silica gel adsorption, and Sephadex G-10 gel filtration. $LC_{90}$ of the partially purified substance against M incognita was $1.2\;{\mu}g/ml$. The nematicidal substance was stable by heat treatment at $100^{\circ}C$ for 1hr, but was perfectly lost nematicidal activity after autoclave ($110^{\circ}C$, 30 min).

• Journal of Microbiology and Biotechnology
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• v.23 no.1
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• pp.88-91
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• 2013

The Cyt1Aa protein of Bacillus thuringiensis subsp. israelensis is known to synergize mosquitocidal proteins of B. thuringiensis and Bacillus sphaericus strains. Cyt1Aa is highly lipophilic, and after binding in vivo to the midgut microvillar membrane serves as a "receptor" for mosquitocidal Cry proteins, which subsequently form cation channels that kill mosquito larvae. Here we report that Cyt1Aa can serve a similar function for lepidopteran-specific Cry proteins of B. thuringiensis in certain mosquito larvae. Engineering Cyt1Aa into the HD-1 isolate of B. thuringiensis subsp. kurstaki enhanced toxicity against $4^{th}$ instars of Aedes aegypti, but not against $4^{th}$ instars of Culex quinquefasciatus.

• Microbiology and Biotechnology Letters
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• v.25 no.6
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• pp.566-570
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• 1997

During sporulation, Bacillus thuringiensis strains produce crystals consist of toxin proteins highly specific against insect pests. Their host specificities are desirable from a standpoint of environmental safety, but also limit market potential. Thus, development of improved Bacillus thuringiensis strains having broad host spectrum will contribute to increase its use. For the construction of Bacillus thuringiensis strain having broad host spectrum, we cloned cry1C gene encoding a toxin protein highly toxic against Spodoptera exigua from a B. thuringiensis isolate and constructed two recombinant plasmids, pUBClC and plC60. The plasmid PUBC1C has a replication origin of the natural plasmid pBC16 from B. cereus which is closely related species to B. thuringiensis, and the pBC16 was known to be replicated by rolling-circle mechanism. The plasmid pIC60 has a replication origin of a resident 60 MDa plasmid from B. thuringiensis subsp. kurstaki HD263, and it is believed that the pIC60 is replicated in a theta mode. The two plasmids were introduced into B. thuringiensis subsp. kurstaki cryB strain, and the transformed strains produced well-shaped bipyramidal crystals. We confirmed the expression of the cry1C gene by SDS-PAGE, and Western blotting. By investigating the segregational stability, it was found that the plasmid pIC60 is more stable than the pUBC1C.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.233-236
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• 2000

Bacillus thuringiensis (Bt) is the most widely used microbial insecticide in the biological control market. Cultivation of the microorganism to high cell densities offers potential for enhancing the rate of formation as well as the concentration of the desired products In the fermentation broths in bioreactor. With this objective, we developed the new bioreactor incorporating ceramic membrane module for the retention of cell mass. Cell yield and spore formation of Bacillus thuringiensis was improved markedly by adopting this new bioreactor based on glucose -limited feeding operation. It was possible to grow the cell and the heat-resistant spore to above $1.2\;{\times}\;10^{10}\;CFU/ml$ density. With glucose-limited operation, we studied the growth behavior of Bacillus thuringiensis during the cell retention culture. Linear growth of Bacillus thuringiensis was observed under glucose-limited culture, which matched well with simple mathematical model of cell retention culture.