• KSBB Journal
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• v.30 no.3
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• pp.132-139
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• 2015

In order to use the symbiotic bacteria from ethomophatogenic nematodes as a biological control agent for agriculture, the cultural condition for maintaining phase I and antifungal activity was investigated. Symbiotic bacteria (SB) 1 stain from nematodes were selected from the three strains isolated from entomopathogenic nematodes. The growth of the SB 1 strain in NB, TSB, TY and YS medium was higher than that of the SB 2 and SB 3 strain. The packed cell volume of the SB 1 strain was reduced in NB medium which showed radical pH change. Phase I of the SB 1 strain was maintained in TSB medium after being stored for 2 weeks at $4^{\circ}C$. Culture broth with the SB 1 strain in TSB medium for 6 days and 7 days showed antifungal activities against Rhizoctonia solani KACC 40142, Botrytis cinerea Pers. KACC 40854, and Botrytis cinerea Pers. KACC 41008. Culture broth with the SB 1 strain in TSB medium containing 100 mM L-proline for 5 days showed antifungal activities against Rhizoctonia solani KACC 40142, and Botrytis cinerea Pers. KACC 40854.

• Korean Journal Plant Pathology
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• v.12 no.1
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• pp.58-65
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• 1996

한국의 수도 재배 지대에서 문제가 되는 다년생 논잡초 올방개에 자연상태에서 기주특이적으로 기생하여 올방개 줄기를 고사시키는 병원균인 Epicoccosorus nematosporus를 우리나라에서 처음으로 분리, 동정하였으며, 이 병을 올방개 지문무늬병(Finegerprint stem blight disease of water chestnut)으로 명명하였다. 분생포자는 분생자층 위에서 형성이 되며 무격막, 단핵이며, 44.5~72 $\mu\textrm{m}$ 크기의 양끝이 뾰족한 선충 모양이다. 갈색의 병반상에서 흑색의 분생자층은 발달하여 특이한 지문무늬를 형성하는 것이 특징이다. 이 병균은 전국의 올방개가 자라는 논에서 분포하며 매년 발생한다. 온실 접종시 초기의 병징은 접종후 4~5일만에 바늘끝 모양의 회흑색의 반점으로 나타나며 시간이 경과하면서 병반은 급속도로 진전하여 접종후 10~15일 정도 후 약 10mm 내외의 갈색병반이 형성이 되어 올방개 줄기를 감싸고 그 줄기 전체는 고사하게 된다. 분생포자 현탁액(3.2$\times$10\ulcorner conidia/ml)을 온실 조건하에서 분무접종 하였을 때 20일 이내에 약 78.0~93.3% 정도의 고사율을 나타내었다. 올방개 지문무늬병균의 분생포자 현탁액(3.2$\times$10\ulcorner conidia/ml)을 온실 조건하에서 벼 등 31개 작물과 피 등 15개 잡초의 유묘에 접종하였을 때 올방개를 제외한 어떤 식물에도 병원성이 없었다.

• The Korean Journal of Mycology
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• v.46 no.1
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• pp.58-68
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• 2018

Sunn hemp (Crotalaria juncea) is used as a nitrogen-fixing green manure in Korea to improve soil quality, reduce soil erosion, and suppress weeds and nematodes. In 2014, wilting sunn hemp plants were observed in green manure-cultivated fields in Wanju, Korea. Leaves of the infected plants began yellowing, starting with the lower leaves, eventually leading to their death. Moreover, a number of dark perithecia were observed on the wilting stems. Six isolates were obtained from these perithecia by single spore isolation. Based on their morphological characteristics, the isolates were identified as Fusarium udum (teleomorph: Gibberella indica). Macroconidia were slightly curved with almost hooked apical cell, and microconidia were formed on false heads by monophialides. Chlamydospores were produced abundantly in the hyphae, either singly or in clusters. To confirm the identification, multilocus sequence analysis was conducted using translation elongation factor 1 alpha (TEF), calmodulin (CAL), and histone 3 (HIS3). The sequences of TEF, CAL, and HIS3 showed 94.4~96.2%, 99.7%, and 99.6~99.8% similarity to the reference sequences of F. udum in NCBI GenBank, respectively. Pathogenicity was tested on sunn hemp and two soybean cultivars using the inoculation method of soil drenching with spore suspension. The wilting symptoms were observed only in sunn hemp and one cultivar of soybean (cv. Teagwang) after 14~21 days of inoculation. This is the first report of wilt disease in sunn hemp caused by Fusarium udum in Korea.

• Parasites, Hosts and Diseases
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• v.36 no.2
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• pp.99-108
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• 1998

The present study was performed to check the viability of eggs, filariform larvae and adults of Strongvloines venezueLensis exposed to various conditions for an in vitro maintenance. The eggs in the feces remained viable for about 25 days at $4^{\circ}C$ and 15 days at room temperature. However, the isolated eggs in sterile saline lost their viability within 24 hr at $4^{\circ}C$. The eggs in morula stage were very sensitive to air drying and rapidly lost their viability (=12 hrs. Filariform larvae survived for a maximum period of 45 days in fecal suspension and 28 days in 0.12% nutrient broth in polyvinyl culture bags maintained at $20^{\circ}C$. On the other hand, those isolated from nutrient broth cultures survived for a maximum period of 32 days in tap water and 22 days in sterile saline at $20^{\circ}C$. The mature adult worms obtained from experimentally infected rats survived maximally for 9 days in serum supplemented (10% rat-serum) 0.12% nutrient broth and 4 days in serum free nutrient broth at $37^{\circ}C$ while the culture media were changed at an alternate day. The adult female worms deposited fertile eggs in serum supplemented and serum free nutrient broth cultures, however, the hatched larvae (Ll) were not able to develop to the filariform stage in the culture media and found to die within 24 hr of maintenance. The present findings on an in vitro maintenance of different stages of 5. uenezueLetis may provide useful information for biological and biochemical studies with Strongyloines species. Key words: Strongvloides venezuelensis. viability in vitro maintenance, free-living filariform larvae (L3), embryonation of eggs

• FLOWER RESEARCH JOURNAL
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• v.19 no.3
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• pp.144-150
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• 2011

This study was carried out to develop the soil amendment practice by phosphate solubilizing bacteria application in greenhouse chrysanthemum cultivation area with high salt accumulation. The experimental site (ShinWoo Flower, GwangJu) has been cultivated chrysanthemum for 15 years and showed significant salt accumulation. The phosphate solubilizing bacteria, Pseudomonas putida (KSJ11), Acinetobacter calcoaceticus (KSJ3) and Acinetobacter calcoaceticus (WP20) formulated on vermiculite for easy use, were applicated. Each 250L of phosphate solubilizing bacteria was applied for $82m^2$ before planting. Acinetobacter calcoaceticus (KSJ3; WP20) increased the amount of soluble phosphorus in an effective level. Particularly, Acinetobacter calcoaceticus (WP20) increased not only the level of soluble phosphorus but also potassium, calcium and magnesium resulting in the increase of EC in the soil. The level of nematode was also decreased with the non-treated increased. As a result, we suggest that selected phosphate solubilizing bacteria (WP20) could be a useful practice for soil amendment in chrysanthemum plantation soil and provided an opportunity to reduce the use of the fertilizer during the cultivation period.

• Korean Journal of Pharmacognosy
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• v.45 no.4
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• pp.275-281
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• 2014

After harvesting the medicinal parts of Curcuma longa, the remaining underground parts were discarded. From the remaining underground parts of Curcuma longa quercetin-3-O-${\beta}$-D-glucopyranoside-7-O-${\alpha}$-L-rhamnopyranoside (Q37) was isolated. The antioxidant activities in vitro and lifespan-extension effect of Q37 were elucidated using the Caenorhabditis elegans. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect of Q37 showed similar potent activities in comparison with vitamin C. Q37 also showed potent superoxide quenching activities as measured by the riboflavin- and xanthine-originated superoxide quenching activity tests. Q37 prolonged lifespan of worms under normal culture condition. In terms of protective effect of Q37 on the stress conditions such as thermal and oxidative stresses, Q37-treated worms exhibited enhanced survival rate, as compared to control worms. To know the possible mechanism of Q37-mediated increased lifespan and stress resistance of worms, we examined the activities of Q37on superoxide dismutase (SOD), and invested intracellular reactive oxygen species (ROS) levels. The results revealed that Q37 was able to elevate SOD activity of worms and reduce intracellular ROS accumulation in a dose-dependent manner.

• Korean Journal of Pharmacognosy
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• v.46 no.1
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• pp.17-22
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• 2015

Previous phytochemical studies of Vigna angularis (Ohwi) Ohwi & Ohashi (Leguminosae) have shown the presence of saponins and flavonoids. From the seed of V. angularis, genistein-7-O-${\beta}$-D-glucopyranoside (genistin) was isolated. Lifespan-extending effect of genistin was elucidated using Caenorhabditis elegans model system. Genistin showed potent lifespan extension of worms under normal culture condition. This compound also exhibited the protective effects against thermal and oxidative stress conditions. In the case of heat stress, genistin-treated worms exhibited enhanced survival rate, compared to control worms. In addition, genistin-fed worms lived longer than control worms under oxidative stress induced by paraquat. To verify the possible mechanism of genistin-mediated increased lifespan and stress resistance of worms, we investigated whether genistin might alter superoxide dismutase (SOD), catalase activities and intracellular ROS levels. Our results showed that genistin was able to elevate SOD and catalase activities of worms and reduce intracellular ROS accumulation in a dose-dependent manner.

• 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.

• KSBB Journal
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• v.15 no.1
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• pp.100-105
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• 2000

Optimal medium composition, culture conditions, characteristics of phase variation and activity of insecticidal toxin by Xenorhabdus nematophilus isolated and identified from Korean entomopathogenic nematode Steinernema carpocapsae were examined. Optimal medium composition of this strain was 50-70 g/L yeast extract, 3 g/L $K_{2}HPO_{4}$, 1g/L $NH_{4}H_{2}PO_{4}$, 2g/L ${MgSO}_4$$\cdot$${7H}_{2}O$, 10g/L NaCl and, these, yeast extract was found as a limiting nutrient for cell growth. When Monod equation was applied, maxmum specific growth rate and Monod constant were estimated as 0.13 $hr^{-1}$ and 20g/L, respectively. The pH of culture medium increased up to 8.5-9.5 regardless of initial pH 6-7 as the cells continued to grow. The specific growth rate in a 7 L fermentor was 0.18 $hr^{-1}$, which was enhancement 1.4 fold compared to a flask culture. In case of phase variation, phase I fraction was maintained above 90% at the stationary phase for both flask and fermentor cultures. According to oral toxicity test of Gallena mellonella by Xenorhabdus nematophilus, the addition of cell pellets into feed inhibited normal growth of insect larvae and killed completely then after 20 days cultivation. When culture supernatant of this strain was injected into hemolymph of insect larva, the toxicity was strongest at 24hr cultivation in the early exponential phase and gradually decreased as the culture time proceeded.

• The Korean Journal of Pesticide Science
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• v.12 no.2
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• pp.184-191
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• 2008

Entomopathogenic bacteria (Xenorhabdus nematophila, X. sp. and Photorhabdus temperata subsp. temperata) isolated from entomopathogenic nematodes express potent insecticidal activity in insect hemocoel. They are also known to suppress insect immune mediation by inhibiting phospholipase $A_2$, leading to host immunosuppression. This study analyzed effects of their cultured broths on inhibiting insect immunosuppression. For this, we removed all bacterial cells using $0.2\;{\mu}m$ pore sized membrane from the bacteria-cultured broth. All three sterilized cultured media, in dose-dependent manners, significantly inhibited hemocyte-spreading behavior of 5th instar larvae of Spodoptera exigua. However, they showed differential inhibitory activities among different bacterial species, in which X. nematophila showed the most potent inhibitory activity. This immunosuppressive effect was applied to increase the pathogenicity of Bacillus thuringiensis (Bt). All three bacterial cultured broths including bacterial cells significantly potentiated Bt pathogenicity against young S. exigua larvae when each of them was orally administered in a mixture of low dose of Bt. Finally, we tested the effect of oral administration of the cultured media containing the immunosuppressive compound(s) secreted by the bacteria. The membrane-sterilized cultured broths were mixed with the low dose of Bt and then orally administered to the young S. exigua. Only the cultured medium of X. nematophila showed increase of Bt pathogenicity. These results indicated that the; cultured media of the three bacteria possessed immunosuppressive factor(s), which may act to potentiate Bt toxicity to young S. exigua larvae.