• The Plant Pathology Journal
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• 제24권4호
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• pp.461-468
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• 2008

An endophytic bacterial strain YC5480 producing antifungal and phytotoxic compounds simultaneously was isolated from the surface sterilized root of Artemisia sp. collected at Jinju area, Korea. The bacterial strain was identified as a species of Pseudomonas brassicacearum based on its 16S rRNA gene sequence analysis and physiological and biochemical characteristics. The seed germination and growth of monocot and dicot plants were inhibited by culture filtrate (1/10-strength Tryptic Soy Broth) of the strain. The germination rate of radish seeds in the culture filtrate differed in various culture media. Only 20% of radish seeds germinated in the culture media of 1/2 TSB for 5 days incubation. Mycelial growth of fungal pathogens, Colletotrichum gloeosporioides, Fusarium oxysporum and Phytophthora capsici was also inhibited by the culture filtrate of the strain YC5480. An antifungal compound, KS-1 with slight inhibitory activity of radish seed germination at 1,000 ppm and a seed germination inhibitory compound, KS-2 without suppression of fungal growth were produced simultaneously in TSB. The compounds KS-1 and KS-2 were identified to be 2,4-diacetylphloroglucinol (DAPG) and 2,4,6-trihydroxyacetophenone (THA), respectively.

• 농업과학연구
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• 제47권4호
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• pp.1071-1081
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• 2020

Essential oils (EOs) have been shown to be plant-extracted antimicrobial agents. However, there are limited studies investigating the efficacy of EOs against pathogens. Among them, tea tree oil (TTO) is extracted from Melaleuca alternifolia, which is also used as an antifungal agent. In this study, the effect of TTO was investigated on the suppression of melon powdery mildew caused by Podosphaera xanthii and tomato leaf mold disease caused by Passalora fulva. Both powdery mildew and leaf mold diseases were significantly suppressed by a spray of TTO. Eighty percent of powdery mildew and 81% of leaf mold disease of the control value were suppressed by 0.5% TTO liquid, when sprayed 3 times every 7 days on the melon and tomato leaves. Inhibition of mycelial growth was also greatly affected by different concentrations of TTO against four different fungal pathogens. Ninety-eight percent of Pseudocercospora fuligena, 97% of P. fulva, 95% of Botrytis cinerea, and 94% of Phytophthora infestans mycelial growth were inhibited by 0.2% to 1.0% of TTO contained in plate media, respectively. However, phytotoxicity in plants by the TTO treatments was revealed when melon and tomato leaves were sprayed with a 1% and 2% concentration of TTO, respectively. Therefore, our findings show that TTO has high antifungal effects against various plant pathogens that occur during crop cultivation. We also suggest that when applying TTO to plant leaves, it is necessary to establish an accurate treatment concentration for different crops.

• Bulletin of the Korean Chemical Society
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• 제32권11호
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• pp.3996-4000
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• 2011

In an attempt to find a new class of anti microbial agents, a series of thiazolidinone and their 5-arylidene derivatives containing 4-(4-methyl benzamido)-benzoyl moiety were synthesized via the reaction of benzocaine with appropriate chemical reagents. These compounds were screened for their antibacterial activity against Gram-positive bacteria (Bacillus subtilis and Bacillus thuringiensis), Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and antifungal activity against Botrytis fabae, Fusarium oxysporan and Candida albicans. On the other hand the synthesized compounds were also screened for their anti tubercular activity. IR, $^1H$ NMR, $^{13}C$ NMR and MS spectral analyses established the structures of the newly synthesized compounds. The results revealed that some of these compounds have shown promising antimicrobial and anti tubercular activity in comparison with standard drugs.

• The Plant Pathology Journal
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• 제22권3호
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• pp.289-294
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• 2006

Two isolates of mucous bacteria, mc75 and pc78, were isolated from fungal culture plate as culture contaminants with an interesting swarming motility. Both isolates were identified as Pseudomonas fluorescens based on microscopy, biochemical analysis, Biolog test and DNA sequence analysis of the 16S rRNA gene. Both strains have the exactly the same 16S rRNA gene sequences, and yet their biological control activity were not identical each other. In vitro analysis of antagonistic activity of two isolates against several plant pathogenic fungi indicated that both produced diffusible and volatile antifungal compounds of unknown identities. Treatment of the bacterial culture of P. fluorescens pc78 and its culture filtrate exhibited a strong biological control activity against rice sheath blight in vivo among six plant diseases tested. More effective disease control activity was obtained from treatment of bacterial culture than that of culture filtrate. Therefore, in addition to antifungal compound and siderophore production, other traits such as biofilm formation and swarming motility on plant surface may contribute to the biological control activity of P.fluorescens pc78 and mc75.

• Journal of Microbiology and Biotechnology
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• 제32권1호
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• pp.37-45
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• 2022

The fungal cell wall and membrane are the principal targets of antifungals. Herein, we report that myricetin exerts antifungal activity against Candida albicans by damaging the cell wall integrity and notably enhancing the membrane permeability. In the presence of sorbitol, an osmotic protectant, the minimum inhibitory concentration (MIC) of myricetin against C. albicans increased from 20 to 40 and 80 ㎍/ml in 24 and 72 h, respectively, demonstrating that myricetin disturbs the cell wall integrity of C. albicans. Fluorescence microscopic images showed the presence of propidium iodide-stained C. albicans cells, indicating the myricetin-induced initial damage of the cell membrane. The effects of myricetin on the membrane permeability of C. albicans cells were assessed using crystal violet-uptake and intracellular material-leakage assays. The percentage uptakes of crystal violet for myricetin-treated C. albicans cells at 1×, 2×, and 4× the MIC of myricetin were 36.5, 60.6, and 79.4%, respectively, while those for DMSO-treated C. albicans cells were 28.2, 28.9, and 29.7%, respectively. Additionally, myricetin-treated C. albicans cells showed notable DNA and protein leakage, compared with the DMSO-treated controls. Furthermore, treatment of C. albicans cells with 1× the MIC of myricetin showed a 17.2 and 28.0% reduction in the binding of the lipophilic probes diphenylhexatriene and Nile red, respectively, indicating that myricetin alters the lipid components or order in the C. albicans cell membrane, leading to increased membrane permeability. Therefore, these data will provide insights into the pharmacological worth of myricetin as a prospective antifungal for treating C. albicans infections.

• The Plant Pathology Journal
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• 제15권1호
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• pp.14-20
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• 1999

Twenty isolates of Helminthosporium species were obtained from various grass plants and tested for controlling efficacy on the development of plant diseases. An isolate of Helminthosporium sp. TP-4 was chosen and six antibiotic substances were purified from cultures of the fungus by repeated silica gel column chromatography and preparative thin-layer chromatography. They were identified as ophiobolin a, 6-epiophiobolin A, 3-anhydroophiobolin A, 3-anhydro-6-epiophiobolin A, iphiobolin B, and iphiobolin I mainly by mass spectrometry and nuclear magnetic resonance spectrometry. Ophiobolins inhibited the growth of a grampositive bacterium Streptomyces griseus, but were not active against gram-negative bacteria. They also showed an antifungal activity. In in vivo tests, iphiobolin B exhibited potent controlling activities against rice blast, tomato late blight, and wheat leaf rust with control values more than 90% and 70% at concentration of $500\mu\textrm{m}$/ml and 100 ${\mu}{\textrm}{m}$/ml. Ophiobolin A and 6-epiophiobolin A controlled the development of wheat leaf rust more than 80% at concentrations of 100 /ml and $500\mu\textrm{m}$/ml respectively. 3-Anhydro-6-epiophiobolin A was not active against any plant disease. On the other hand, the A-series ophiobolins other than 3-anhydroophiobolin A showed stronger phytotoxic activity in a leaf-wounding assay using 8 plant species than those of 3-anhydroophiobolin A, ophiobolin B, and ophiobolin I. The results indicate that there is little correlation between antifungal activity and phytotoxicity of ophiobolins.

• The Plant Pathology Journal
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• 제25권4호
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• pp.344-351
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• 2009

A biocontrol bacterium Bacillus licheniformis N1 grown in nutrient broth showed no chitinolytic activity, while its genome contains a gene which encodes a chitinase. The gene for chitinase from B. licheniformis N1 was amplified by PCR and the deduced amino acid sequence analysis revealed that the chitinase exhibited over 95% identity with chitinases from other B. licheniformis strains. Escherichia coli cells carrying the recombinant plasmid displayed chitinase activity as revealed by the formation of a clear zone on chitin containing media, indicating that the gene could be expressed in E. coli cells. Chitinase gene expression in B. licheniformis N1 was not detected by RT-PCR analysis. The protein was over-expressed in E. coli BL21 (DE3) as a glutathione S-transferase fusion protein. The protein could also be produced in B. subtilis 168 strain carrying the chitinase gene of N1 strain. The crude protein extract from E. coli BL21 carrying GST fusion protein or culture supernatant of B. subtilis carrying the chitinase gene exhibited enzyme activity by hydrolyzing chitin analogs, 4-methylumbelliferyl-$\beta$-D-N,N'-diacetylchitobioside and 4-methylumbelliferyl-$\beta$-D-N,N',N"-triacetylchitotrioside. These results indicated that even though the chitinase gene is not expressed in the N1 strain, the coding region is functional and encodes an active chitinase enzyme. Furthermore, B. subtilis 168 transformants expressing the chitinase gene exhibited antifungal activity against Fulvia fulva by suppressing spore germination. Our results suggest that the proper engineering of the expression of the indigenous chitinase gene, which will lead to its expression in the biocontrol strain B. licheniformis N1, may further enhance its biocontrol activity.

• Journal of Microbiology
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• 제45권5호
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• pp.460-465
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• 2007

This study was carried out in order to investigate the potential of using plant oils derived from Leptospermum petersonii Bailey and Syzygium aromaticum L. Merr. Et Perry as natural antifungal agents. The antifungal effects of essential oils at concentrations of 0.05, 0.1, 0.15, and 0.2 mg/ml on the dermatophytes Microsporum canis (KCTC 6591), Trichophyton mentagrophytes (KCTC 6077), Trichophyton rubrum (KCCM 60443), Epidermophyton floccosum (KCCM 11667), and Microsporum gypseum were evaluated using the agar diffusion method. The major constituents of the active fraction against the dermatophytes were identified by gas chromatography-mass spectrometry and high-performance liquid chromatography analysis. The antifungal activities of S. aromaticum oil (clove oil) against the dermatophytes tested were highest at a concentration of 0.2mg/ml, with an effectiveness of more than 60%. Hyphal growth was completely inhibited in T. mentagrophytes, T. rubrum, and M. gypseum by treatment with clove oil at a concentration of 0.2 mg/ml. Eugenol was the most effective antifungal constituent of clove oil against the dermatophytes T. mentagrophytes and M. canis. Morphological changes in the hyphae of T. mentagrophytes, such as damage to the cell wall and cell membrane and the expansion of the endoplasmic reticulum, after treatment with 0.11 mg/ml eugenol were observed by transmission electron microscopy (TEM). At a concentration of 0.2 mg/ml, L. petersonii oil (LPO) was more than 90% effective against all of the dermatophytes tested, with the exception of T. rubrum. Geranial was determined to be the most active antifungal constituent of L. petersonii oil. Taken together, the results of this study demonstrate that clove and tea tree oils exhibited significant antifungal activities against the dermatophytes tested in this study.

• Journal of Microbiology and Biotechnology
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• 제14권5호
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• pp.1067-1070
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• 2004

In the course of screening for specific inhibitors against the mycelial form of Candida albicans from natural resources, we have isolated and identified A6792-1 from Streptomyces sp. A6792 by using several chromatographies. By spectral analyses, this compound was determined as 7-oxostaurosporine, having a structure of staurosporine aglycon noiety. 7-Oxostaurosporine exhibited a selective growth inhibitory activity against the mycelial form of Candida spp. up to $100\mu\textrm{g}/disc$ in bioassay. It also exhibited a specific antifungal activity against the mycelial form of Candida spp. including C. krusei, C. albicans, C. tropicalis, and C. lusitaniae with MICs ranging from 3.1 to $25\mu\textrm{g}/ml$ 7-Oxostaurosporine demonstrated no in vivo toxicity in SPF ICR mice. Therefore, this compound may have a considerable potential as an antifungal agent based on the preferential inhibition against growth of the mycelial form of Candida spp., dimorphic fungi.

• 한국미생물·생명공학회지
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• 제29권4호
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• pp.253-257
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• 2001

편백의 정유성분을 추출하여 수종의 병원성세균과 진균을 대상으로 항세균 및 항진균효과를 실험하여 다음과 같은 결과를 얻었다. 편백정유는 그람 양성균인 S epidermidis, 그람 음성균인 V parahemolyticus와 P. aeruginosa에 대해서는 200 ppm부터 항세균효과를 나타냈고, P putida에 대해서는 400ppm 부터 항세균효과를 나타냈다. 항세균효과가 나타난 균주들은 편백정유의 농도가 증가할수록 효과가 높게 나타났으며 통계적으로 유의성이 관찰되었다(p<0.05) 또한 편백정유는 효모형 곰팡이인 C, albicans에 대하여 200 ppm부터 항진균효과를 나타냈으며, 사상형 곰팡이인 A, mali와 A, nidulans에 대해서는 400 ppm부터 F. oxyporum 에 대해서 100 ppm 부터 항진균효과를 보였고 편백정유의 농도가 증가할수록 균주의 성장억제대가 증가되었다. 따라서 편백을 항균제나 방부제로 사용할수 있는 가능성을 확인하였다.