• Microbiology and Biotechnology Letters
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• v.27 no.5
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• pp.359-363
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• 1999

To prevent appearance of resistant mosquitoes against $\delta$-endotoxin of bacillus thuringiensis subsp. israelensis (Bti) in field, a mosquitocidal Bacillus thuringiensis strain 21-2(Bt21-2) producing a new type of $\delta$-endotoxin was isolated. The strain Bt 21-2 belongs to H serotype 43, B. thuringiensis subsp. guiyangiensis (Btg). The $\delta$-endotoxins from the strain Bt 21-2 and the strain Bti were a cuboid shape morphologically, but the $\delta$-endotoxin of the strain Bt 21-2 was composed of 150, 90 and 70kDa proteins on SDS-PAGE, and the antigenicity of $\delta$-endotoxin of the strain Bt 21-2 was different from that of the strain Bti on immunoblot. The $\delta$-endotoxin gene of the strain Bt 21-2 was not amplified with specific primers of $\delta$-endotoxin gene (cry4A and cry4B) of the strain Bti on PCR.

• Microbiology and Biotechnology Letters
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• v.22 no.3
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• pp.227-232
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• 1994

In order to microbially control root-knot nematode(Meloidogyne incognita) in tomato, a strain BtTH109 of Bacillus thuringiensis producing root-knot nematocidal toxin was isolated. The strain BtTH109 was identified B. thuringiensis subsp. indiana(serotype 16) based on flagella antigenicity, biochemical properties, and morphological charcateristics. The strain BtTH109 have extracellularly produced a root-knot nematocidal toxin, which was very toxic against not only egghatch but also the 2nd-nematode larva of root-knot nematode in vitro.

• 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.

• Journal of Sericultural and Entomological Science
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• v.37 no.1
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• pp.62-67
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• 1995

Ultrastructural changes of tissues caused by Bacillus thuringiensis var. kurstaki $\delta$-endotoxin intoxication of Hyphantria cunea were observed by transmission electron microscopy. Bt $\delta$-endotoxin crystals induced the disruption of microvilli, vacuolation of cytoplasm, changes in the cisternae of the endoplasmic reticulum, disappearance of basal striations, loss of ribosomes, and changes in the configurations of mitochondria in the columnar cell of midgut. The fat body cells also showed spherical endoplasmic reticulum and distorted mitochondria, and then the cells were destroyed.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.322-326
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• 1994

Bacillus thuringiensis strain BT-14 was isolated from alfalfa dust in Korea. The strain BT-14 produced one bipyramidal crystal and one spore in the cell. The biochemical characteristics of the strain BT-14 were similar to those of Bacillus thuringiensis subsp. kurstaki HD-l. Examination of its antibiotic resistance revealed that while the strain BT-14 was less resistant than BTK HD-l to ampicillin, gentamycin, neomycin and tobramycin, it was more resistant to amikacin than BTK HD-l. The $\delta$-endotoxin crystal of strain BT-14 consisted of a single protein with a high molecular weight of ca 135 KD on a 10% SDS-PACE. The strain BT-14 contained at least nine different plasmids with sizes of 2.9, 5.3, 5.8, 6.2, 9.4, 15.1, 18.1, 23.1 and 79 Kb. In insect bioassay, the isolated strain BT-14 showed lethality of 67% against Plutella xylostella larvae at dilution of 5$\times$$l0^{-4}$ (5$\times$l0 to 3$\times$$l0^2$ spores/ml), which is, almost equivalent to that of BTK HD-l.

• Journal of Microbiology and Biotechnology
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• v.5 no.3
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• pp.138-142
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• 1995

Bacillus thuringiensis strain BT-209 was isolated from a soybean grain dust sample in Korea. The strain BT-209 produced two different sizes of cuboidal crystals and one spore in the cell. In the biochemical characterization, the strain BT-209 showed negative reactions on the production of urease, and the utilization of citrate and sucrose. Examination of its antibiotic resistance revealed that while the strain BT-209 showed higher sensitivity than B. thuringiensis subsp. kurstaki HD-1 to ampicillin, bacitracin, chlortetracycline, gentamycin, neomycin, penicillin G, tetracycline and tobramycin, it was more resistant to methicillin than B. thuringiensis subsp. kurstaki HD-1. The $\delta$-endotoxin crystal of strain BT-209 consisted of three proteins with apparent molecular weights of appoximately 148, 135 and 62 kDa on a 10% SDS-PAGE. The strain BT-209 had at least eight different plasmids with sizes of 4.1, 5.2, 6.3, 8.6, 14.6, 24.5, 67.6 and 77.6 Kb. The strain BT-209 showed strong lethalities of 70% and 87% against Bombyx mori and Hyphantria cunea larvae. at 72 h, respectively.

• Microbiology and Biotechnology Letters
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• v.22 no.6
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• pp.679-684
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• 1994

For a biological control of root-knot nematode (Meloidogyne incognita) in tomato, efficiency of Bacillus thuringiensis subsp. indiana strain TH109 (BtTH109) on the nematode control was investigated. After the mixture of strain BtTH109 and wheat bran was treated into rhizosphere of the tomato plants with nematode eggs, the stem height and root growth of plants increased. And the juveniles and eggs of nematode are not found in both roots of tomatoes and pot soil after cultured broth of the strain BtTH109 treated 4 times at 3 day-interval into rhizosphere of the infected tomatoes.

• Korean Journal of Microbiology
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• v.46 no.4
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• pp.389-396
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• 2010

Insecticidal crystalline toxin producing Bacillus thuringiensis BT17 strain was isolated and identified as B. thuringiensis serovar colmeri by 16S rRNA analysis. BT17 strain produced crystalline ${\delta}$-endotoxin against to Lepidopteran larvae effectively on the culture broth of soybean meal and skim milk, $30^{\circ}C$ and 36 h shaking culture of 280 rpm. The maximum colony forming unit achieved when the culture was continued for 24 h, but the number of crystals increased until 36 h in the 200 L fermentor. Liquid type of biological insecticide product was made, and after 3 months storage in $20^{\circ}C$ the number of crystals was increased up to twice than beginning. Biocontrol effect of BT17 insecticide product was better in Plutella xylostella than in Spodoptera exigua, and the toxicity to animals was negligible.

• Journal of Life Science
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• v.17 no.5 s.85
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• pp.658-663
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• 2007

Bacillus thuringiensis is a well-known species of entomophathogenic bacteria that is widely used as a biopesticide against many insect pests. It produces parasporal crystals ($\delta$-endotoxin) and endospores during sporulation. In this report, the $\delta$-endotoxin produced by Bacillus thuringiensis BT-1 and BT-2 were characterized by Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM), SDS-PACE, and solubilization activity by alkaline solution. BT-1, BT-2 were cultured in the GBY medium, and the $\delta$-endotoxin of them was purified with discontinuous sucrose density gradient centrifugation. Their $\delta$-endotoxin was observed by SEM and TEM. Morphologically, the $\delta$-endotoxin of BT-1 was a square and flat type, whose size was $1.73{\mu}m{\times}0.7{\mu}m$, and the $\delta$-endotoxin of the BT-2 was spherical form whose size was $1.1{\mu}m{\times}0.9{\mu}m$ determined by SEM and TEM. The $\delta$-endotoxin of the BT-1 was composed of 28 kDa and 21 kDa, however, it of the BT-2 was composed of 50 kDa, 35 kDa, and 22 kDa bands determined by SDS-PACE. The purified crystals of BT-1 and BT-2 were dissolved gradually in alkaline solution as time goes by, and it was perfectly dissolved after 3 hours. It is supposed that the $\delta$-endotoxin of crystal was converted to a state of activation in the course of time in the intestines of insect.

• The Korean Journal of Pesticide Science
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• v.13 no.2
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• pp.111-116
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• 2009

Juvenile hormone (JH) is an insect hormone mediating immature metamorphosis and adult reproduction. It also mediates immune responses to suppress hemocyte behavior, which is, however, activated by ecdysteroid. This study investigated an effect of a commercial pyriproxyfen (a JH agonist) formulation on a cellular immune response of the diamondback moth, Plutella xylostella, and analysed its mixture with Bacillus thuringiensis (Bt) in insecticidal potency. The commercial pyriproxyfen formulation significantly suppressed hemocyte-spreading behavior at low doses as did in pyriproxyfen technical grade. When the commercial pyriproxyfen formulation was mixed with Bt, Bt toxicity was significantly increased against P. xylostella larvae in laboratory. The mixture effect was then confirmed in field cultivating cabbage infested with P. xylostella larvae. The mixture showed a significantly enhanced mortality and reduced effective lethal time, compared to only Bt treatment.