• Proceedings of the Korean Society of Plant Pathology Conference
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• 1994.06a
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• pp.11-26
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• 1994

Crown gall of stonefruit and nut trees is one of the very few plant diseases subject to efficient biological control. The disease is caused by the soil-inhabiting bacteria Agrobacterium tumefaciens and Agrobacterium rhizogenes and the original control organism was a non-pathogenic isolate of A. rhizogenes strain K84. Control is achieved by dipping planting material in a cell suspension of strain K84 which specifically inhibits pathogenic strains containing a nopaline Ti plasmid. Because the agrocin 84-encoding plasmid (pAgK84) is conjugative, it can be transmitted from the control strain to pathogenic strains which, as a result, become immune to agrocin 84 and cannot be controlled. To prevent this happening, the transfer genes on pAgK84 were located and then largely eliminated by recombinant DNA technology. The resulting construct, strain K1026, is transfer deficient but controls crown gall just as effectively as does strain K84. Field data from Spain confirm that pAgK84 can transfer to pathogenic recipients from strain K84 but not from strain K1026. The latter has been registered in Australia as a pesticide and is the first genetically engineered organism in the world to be released fro commercial use. It is recommended as a replacement for strain K84 to prevent a breakdown in the effectiveness of biological control of crown gall. Several reports indicate that both strains K84 and K1026 sometimes control crown gall pathogens that are resistant to agrocin 84. A possible reason for this is that both strains produce a second antibiotic called 434 which inhibits growth of nearly all isolates of A. rhizogenes, both pathogens and non-pathogens. Crown gall of grapevine is caused by another species, Agrobacterium vitis. It is resistant to agrocin 84 and cannot be controlled by strains K84 or K1026. It is different from other crown gall pathogens in several characteristics, including the fact that, although a rhizosphere coloniser, its also lives systemically in the vascular tissue of grapevine. Pathogen free propagating material can be obtained from tissue culture or, less surely, by heat therapy of dormant cuttings. A number of laboratories are searching for a biocontrol strain that will prevent, or at least delay, reinfection. A non-pathogenic A. vitis strain F/25 from South Africa looks very promising in this regard.

• Journal of Microbiology and Biotechnology
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• v.10 no.3
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• pp.375-380
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• 2000

The preliminary screening of several cyanobacteria, using mice bioassay, reveale the production of a hepatotoxin by the cyanobacterium Scytonema sp. strain BT 23 isolated from soil. An intraperitoneal injection of the crude toxin (LD50 56 mg/kg body wt) from this strain caused the death of the mice within 40 min, and the anmals showed slinical signs of mice within 40 min, and the animals showed clinical signs of hepatotoxicity. The toxin was purified and partially characterized. The active fraction appears to be nonpolar in nature and shows absorption peaks at 240 and 285 nm. The purified toxin had an LD50 of TEX>$100<\mu\textrm{g}/kg$ body wt and the test mice died within 40 min of toxin administration. The toxin-treated mice showed a 1.65-fold increase in liver weight at 40 min and the liver color chnged to dark red due to intrahepatic hemorrhage and pooling of blood. Furthermore, the administration of the toxin to test mice induced a 2.58, 2.63, and 2.30-fold increse in the activity of the serum enzymes alanine aminotransferase, lactate dehydrogenase, and alkaline phosphatase, respectively. Further experiments with the 14C-labeled toxin revealed a maximum accumulation of the toxin in the liver. The clinical symptoms in the mice were similar to those produced by microcystin-L.R. These results suggest that hepatotoxins may also be produced in non bloom-forming planktonic cyanobacteria.

• Geotechnical Engineering
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• v.5 no.2
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• pp.45-56
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• 1989

The influence of stress path on the deformation characteristics of clay has been studied through a series of stress-path controlled triaxial tests on artificially sedimented and normally con- solidated Kaolinite. It has been found that there exists a critical stress increment ratio, Kc, in which stress·strain characteristics possesses a linear relationships and beyond Kc, strain hardening. A modified hyperbolic constitutive model for the strain hardening behavior has been formulated based on the Drnevich's hyperbolic function. And, a method of settlement analyses has been Proposed wherein the effect of stress path during consolidation is taken into account.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.115-118
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• 1988

Mating experiments were performed to, elucidate the distribution of perfect state of Microsporum gypseum complex originated from animals and soils in Korea. A total of 30 strains of M. gypseum complex, composed of 16 from animals and 14 from soils, ere mated with the tester strains of Nannizzia incurvata, N. gypsea and N. fulva. Among 30 strains of M. gypseum complex examined, 16 strains(53.3%) were N. incurvata, 13 strains(43.3%) N. gypsea and 1 strain (3.3%) N. fulva. Among 13 strains of dog isolates, 8 strains(61.5%) were N. incurvata and 5 strains(38.5%) N. gypsea. And each strain isolated from Korean native goat, monkey and albino rat was N. gypsea. Among 14 strains of soil isolates, 8 strains(57.2%) were N. incurvata, 5 strains (35.7%) N. gypsea and 1 strain(7.2%) N. fulva. And -mating type was more frequently observed than +mating type in the strains of N. incurvata and N. gypsea. By this study, N. fulva was isolated the first time in Korea.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.348-361
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• 1991

When reinforcing strip footing on a sand 8round with reticulated root piles, reinforcing effect depends on the length , number, cross sectional area, penetration angle, spacing, and Young's modulus of piles. the mode of action of reinfocement tendons in soil isn't one of carring developed tensile stresses but of anisotropic(uni-directional) reduction or even supression of one normal strain rate. R. H. Bassett and N. C. Last proposed that the reinforcement should be located on the direction of minor strain rate which coincides with the tensile strain rate in the velocity characteristics. Based on this proposal the author carried out a series of 2 - dimentional finite element analysis which varies the parameters mentioned above.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.348-359
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• 2018

A series of indoor simulation tests on a large-sized shaking table was performed, which was used to simulate the earthquake ground motion for the pipe-soil interaction system to be tested. The purpose of this study is to examine the dynamic characteristic and seismic response of a length of PVC pipeline lay on a clay seabed under seismic load. The pipeline was fully instrumented to provide strain and acceleration responses in both transverse and in-line. Dynamical modal tests show that corresponding mode shapes vertically and horizontally are basically the same. But the absolute values of the natural frequencies vertically are all higher than those corresponding values in transverse. It turned out that the geometry configuration of riser affects its stiffness. Seismic response of pipeline depends significantly on the waveform, and Peak Ground Acceleration (PGA). As the seismic loading progressed, the strain response was severe around both TDZ and catenary zone. Additionally, strain responses in top and bottom positions were more severe than the result in left or right side of the pipeline in the same section.

• Journal of Microbiology and Biotechnology
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• v.4 no.2
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• pp.126-133
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• 1994

A Pseudomonas putida strain able to accumulate high amount of polyesters of medium-chain-length 3-hydroxyalkanoic acids ($PHA_{MCL)$) was isolated from soil in a landfill site using an enrichment technique. Culture condition of the isolated strain for polyester production in a one-step culture was optimized in a mineral-salts medium against pH and concentrations of ammonium sulfate, carbon source(e.g., octanoate), and phosphate. The optimal values for maximal cell growth and PHA accumulation were: pH; 7$\sim$8, $(NH_4)_2SO_4$; 8 mM, octanoate; 40 mM. The optimum temperature was in the range of $20\sim30^{\circ}C$, which was rather broader than in other bacteria. Cell growth was strongly inhibited by the phosphate limitation to less than 1 mM. An increase of phosphate concentration above 1 mM showed little effect on cell growth and polyester accumulation. When the strain was grown on octanoate under this optimized condition it produced 3.4 g dry biomass per liter and yielded 1.7 g PHA per liter amounting to 53 wt% of dry cells. The monomer units composing the polyester synthesized from octanoate were 3-hydroxyoctanoate (3HO), 3-hydroxycaproate (3HC), and 3-hydroxybutyrate (3HB) (85:13:2, mole ratio). Other low linear $C_3\simC_{10}$ monocarboxylic acids were also tested for polyester production.

• Journal of Environmental Science International
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• v.3 no.3
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• pp.197-207
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• 1994

Microorganisms capable of utilizing 2,4,5-trichlorophenoxyacetic acid(2,4,5-T) as sole carbon source were isolated from soil by enrichment culture. Among these strains, EL-O7IP had the highest biodegradability of 2,4,5-7, and according to its morphological and physiological characteristics, it was identified as Pseudomonas sp. This strain was resistant to rifampicin, streptomycin, ampicillin, kanamycin and such metal ions as $Zn^{2+}$, $Cu^{2+}$ Various compounds of chlorinated phenol and substrate analogs were more easily utilized than 2,4,5-7, but biodegradation rate for each compound was different. The strain easily utilized the compounds of chlorinated substituents on phenol in the order of ortho-, para-, and meta- position. The biodegradability of this strain was very stable. Key words : 2,4,5- trichlorophenoxyacetic acid, Pseudomonas sp .

• Microbiology and Biotechnology Letters
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• v.24 no.3
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• pp.344-351
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• 1996

Microorganisms growing alcoholic distillery wastes were isolated from soil. Of them, the selected strain EL-9 had a capability of accumulating poly-$\beta$-hydroxybutyrate (PHB) when grown in alcoholic distillery wastes. The strain EL-9 was identified as a genus Actinobacillus based on the morphological, cultural, and biochemical characteristics. The strain EL-9 was named temporarily as Actino- bacillus sp. EL-9. The optimal temperature and pH for cell growth of Actinobacillus sp. EL-9 were 30$\circ$C and 7.0, respectively. The optimal medium compositions for cell growth comprised glucose 2%, NH$_{4}$NO$_{3}$ 0.15%, Na$_{2}$HP0$_{4}$-12H$_{2}$O 0.25%, KH$_{2}$PO$_{4}$ 0.25%, MgSO$_{4}$4-7H$_{2}$O 0.15%, FeSO$_{4}$-7H$_{2}$O 0.005%, CaCl$_{2}$-2H$_{2}$O 0.003% and trace element solution 5m/l. To investigate the optimal conditions for PHB production, two-stage culture technique was used. The result showed that the optimal conditions for PHB production are identical those for cell growth. When propionic acid was added as a cosubstrate, PHB/HV copolymer was produced.

• Microbiology and Biotechnology Letters
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• v.17 no.4
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• pp.289-294
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• 1989

A bacterial strain capable of producing high level of extracellular xylanase was isolated from soil. The characteristics of the isolated strain No.236 were identified to be Bacillus stearothermophilus. The maximal xylanase production was observed in the medium containing 0.75% xylan, 0.35% yeast extract, 1.06% $K_2$HPO$_4$and 0.05% CaCO$_3$with initial pH of 6.5 when the strain was cultured at 5$0^{\circ}C$ for 28 hrs with reciprocal shaking. Hydrolysis of xylan by the xylanase revealed that xylose was the only product of the reaction. This suggested that the enzyme produced by Bacillus stearothermophilus No. 236 was an exe-acting xylanase.