• 식물병연구
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• 제24권4호
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• pp.339-341
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• 2018

Amaranth has the potential for good materials related to nutrients and health benefits. There are several diseases of amaranth such as leaf blight, damping-off, and root rot. As a causal agent of soft rot disease, Pectobacterium spp. could infect various plant species. In this study, we isolated the bacterial pathogen causing soft rot of amaranth in South Korea. In Gangneung, Gangwon province during 2017, amaranth plants showed typical soft rot symptoms such as wilting, defoliation and odd smell. To isolate pathogen, the macerated tissues of contaminated amaranth were spread onto LB agar plates and purified by a single colony subculture. One ml bacterial suspension of a representative isolate was injected to the stem of five seedlings of 2-week-old amaranth with a needle. Ten mM magnesium sulfate solution was used as a negative control. 16S rDNA gene and recA gene were sequenced and compared with the reference sequences using the BLAST. In the phylogenetic tree based on 16S rDNA gene and recA gene, GSA1 strain was grouped in Pcb.

• 식물병연구
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• 제30권1호
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• pp.95-98
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• 2024

In a survey conducted in March 2023, Euphorbia hypogaea plants cultivated within greenhouses in Yongin, Korea exhibited water-soaked areas near the stem base, close to the soil. Subsequent isolation from diseased E. hypogaea led to the identification of a bacterial strain, designated as CBNUMPBL-103. The isolate was identified as Dickeya dadantii through sequencing of the 16s rRNA and phylogenetic analysis. The pathogenicity of the isolate was confirmed by inoculating it into healthy E. hypogaea, resulting in the manifestation of similar symptoms observed during the survey. The re-isolated strain recovered from inoculated plants showed a similar morphology with the inoculated strain. This is the first documentation of D. dadantii causing soft rot of E. hypogaea in Korea.

• 한국작물학회지
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• 제43권2호
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• pp.64-65
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• 1998

The inheritance of resistance to bacterial blight in a Tongil-type rice cultivar 'Changseongbyeo' was studied using a Korean isolate HB9101. which belongs to race $K_1$. The resistance of Changseongbyeo to the HB9101 was controlled by a single dominant gene. This gene was allelic with Xa-1 gene and linked to Ig gene on chromosome 4 with the recombination value of 7.5%.

• 약학회지
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• 제45권3호
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• pp.245-250
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• 2001

Aminoacyl tRNA synthetases of bacteria are known as potential targets for new anti-microbial agents. To isolate new inhibitors of bacterial methionyl-tRNA synthetases from natural sources, a new target-oriented screening system using whole cells which are over-expressing a target enzyme was developed. Approximately 8,000 culture broths of microorganisms from soils were tested by this screening system. Among them, ten culture broths was found to contain inhibitory activity against methionyl -tRNA synthetases of Escherichia coli. For the validation of the screening system, this new method was compared with in vitro enzymatic method. Seven out of 10 culture broths showed inhibitory activity against methionyl-tRNA synthetases of E. coli. This result showed that the new screening system was comparable to the enzyme assay. Thus we believe that our screening system as a new method can be applied for the screening of new antibiotics inhibiting bacterial methionyl-tRNA synthetases from natural products.

• Journal of Microbiology
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• 제39권2호
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• pp.133-138
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• 2001

We investigated the antagonism of indigenous bacteria isolated from stressed mussels and their extracellular metabolites on the adult zebra mussel, Dreissena polymorpha. Selective bacterial isolates including Aeromonas media, A. salmonicida, A. veronii, and Shewanella putrefaciens, showed strong lethality against adult mussels and 100% mortality was observed within 5 days of incubation. Bacterial metabolites, fractionated and concentrated from stationary-phase culture supernatants of these bacterial isolates, displayed varying degrees of antagonistic effects on zebra mussels. Among the three size fractions examined, <5, 5-10, and >10 kDa, the mast lethal fraction seems to be >10 kDa for three of the four isolates tested. Further chemical analyses of these size fractions revealed that the predominant constituents were polysaccharides and proteins. No 2-keto-3-deoxyoctanoic acid (2-KDO), deoxyribonucleic acids (DNA) or uranic acid were detectable. Extraction of supernatants of two antagonistic isolates with polar solvent suggested that polar molecules are present in the active fraction. Our data suggest that extracellular metabolites produced by antagonistic bacteria are also involved in disease development in zebra mussels and elucidation of the mechanisms involved may offer a novel strategy for control of biofouling invertebrates.

• The Plant Pathology Journal
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• 제40권1호
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• pp.1-15
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• 2024

The aim of this study was to isolate biocontrol bacteria that could antagonize brown rot of Dendrocalamus latiflorus, optimize the culture conditions, and develop an effective biocontrol preparation for brown rot of D. latiflorus. This study isolated a bacterium with an antagonistic effect on bamboo brown rot from healthy D. latiflorus rhizosphere soil. Morphology, molecular biology, and physiological biochemistry methods identified it as Bacillus siamensis. The following culturing media and conditions improved the inhibition effect of B. siamensis: the best culturing media were 2% sucrose, 1.5% yeast extract, and 0.7% potassium chloride; the optimal culturing time, temperature, pH, and inoculation amount were 48 h, 30℃, 6, and 20%. The optimum formula of the applying bacterial suspension was 14% sodium dodecyl benzene sulfonate emulsifier, 4% Na₂HPO₄·2H₂O, 0.3% hydroxypropyl methylcellulose thickener, and 20% B. siamensis. The pot experiment results showed the control effect of applying bacterial suspension, diluted 1,000 times is still better than that of 24% fenbuconazole suspension. The applying bacterial suspension enables reliable control of brown rot in D. latiflorus.

• 미생물학회지
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• 제40권1호
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• pp.1-6
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• 2004

대구지역에서 수집한 50점의 김치 중에서 10점의 김치로부터 tetracycline내성 세균을 분리하였다. 이 균주들의 tetracycline에 대한 MIC는 25-100 mg/l 이상의 범위로 분포하였으며 다른 항생제에 대한 내성도 다양하였다. tet(M), tet(O)특이적 primer를 이용한 PCR에서 HJ9 한 균주에서만 tet(M)유전자가 검출되었으며, tet(M)은 플라스미드상에 존재하는 것으로 나타났다. HJ9 균주의 tet(M)부분 염기서열을 분석한 결과 기존에 보고된 Gram양성균의 tet(M)의 DNA 염기서열 및 아미노산 서열과 각각 90-99%, 94-100%의 높은 상동성을 보였다. 165 rRNA 염기서열을 분석한 결과 HJ9 균주는 Lactobacillus sakei로 동정되었다. 김치를 통하여서도 항생제 내성 유전자의 전파 확산이 가능할 것으로 생각된다.

• Mycobiology
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• 제40권1호
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• pp.59-65
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• 2012

Antagonistic microorganisms against $Rhizoctonia$ $solani$ were isolated and their antifungal activities were investigated. Two hundred sixteen bacterial isolates were isolated from various soil samples and 19 isolates were found to antagonize the selected plant pathogenic fungi with varying degrees. Among them, isolate C9 was selected as an antagonistic microorganism with potential for use in further studies. Treatment with the selected isolate C9 resulted in significantly reduced incidence of stem-segment colonization by $R.$ $solani$ AG2-2(IV) in Zoysia grass and enhanced growth of grass. Through its biochemical, physiological, and 16S rDNA characteristics, the selected bacterium was identified as $Bacillus$ $subtilis$ subsp. $subtilis$. Mannitol (1%) and soytone (1%) were found to be the best carbon and nitrogen sources, respectively, for use in antibiotic production. An antibiotic compound, designated as DG4, was separated and purified from ethyl acetate extract of the culture broth of isolate C9. On the basis of spectral data, including proton nuclear magneric resonance ($^1H$ NMR), carbon nuclear magneric resonance ($^{13}C$ NMR), and mass analyses, its chemical structure was established as a stereoisomer of acetylbutanediol. Application of the ethyl acetate extract of isolate C9 to several plant pathogens resulted in dose-dependent inhibition. Treatment with the purified compound (an isomer of acetylbuanediol) resulted in significantly inhibited growth of tested pathogens. The cell free culture supernatant of isolate C9 showed a chitinase effect on chitin medium. Results from the present study demonstrated the significant potential of the purified compound from isolate C9 for use as a biocontrol agent as well as a plant growth promoter with the ability to trigger induced systemic resistance of plants.

• 한국자원식물학회지
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• 제18권1호
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• pp.198-206
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• 2005

애완견의 털에 부착되어 있는 세균을 분리 동정한 후, 이 분리 세균들에 대한 항세균효과가 있는 생약재 추출물을 탐색하였다. 애완견의 털에서 76개의 세균을 분리한 결과, Staphylococcus속이 41균주로 가장 많았으며 그 다음으로 Micrococcus속이 21균 주, Enterococcus속이 8균주, Bacillus속이 3균주, Exiguobacterium속 of 2균주, Shigella속과 Zoogloea속이 각각 1균주씩으로 동정되었다. 이러한 결과는 개의 털에 존재하는 세균들이 사람에게 감염을 일으킬 수 있는 원인이 될 수 있음을 시사한다. 분리균주들에 대한 항생제 저항성과 생약재 추출물의 항세균 활성은 디스크 확산법으로 확인하였다. 황금의 추출물이 애완견의 털로부터 분리한 세균들에 대해 높은 항세균 활성을 나타내어 항생제 저항성이 있는 세균들에 대한 새로운 항미생물제로 사용학 수 있을 것으로 기대된다.

• 식물병연구
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• 제29권4호
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• pp.433-439
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• 2023

당근 세균잎마름병은 세계적으로 가장 중요한 병에 속한다. 지난 10년 전 국내에서 처음 발견됨으로써 당근 생산에 큰 위협이 되는 병으로 간주되었다. 원인균으로 Xathomonas hortorum pv. carotae (Xhc)이며 본 연구는 제주도 당근재배지 토양에서 이 병원균을 분리 동정하고자 수행하였다. 분리한 세균 중 인공배지에서 균총의 형태가 당근 세균잎마름병균과 유사한 세균균총을 분리하여 선발하였다. 또한 이들 선발된 세균들을 대상으로 DNA 염기 서열과 NCBI 자료를 통해 몇몇 분리 세균이 Xhc으로 동정되었다. 게다가 이들 세균을 당근 잎에 접종하였더니 당근 세균잎마름병의 전형적인 병징이 나타났다. 본 연구 결과는 제주도 토양내 Xhc의 존재 가능성을 시사하고 앞으로의 당근 세균잎마름병 방제 수단을 강구하는 데 매우 필요한 자료로서 가치가 있다고 본다.