• 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.

• Journal of Microbiology and Biotechnology
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• 제24권9호
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• pp.1216-1225
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• 2014

Biofilm-related infections of Candida albicans are a frequent cause of morbidity and mortality in hospitalized patients, especially those with immunocompromised status. Options of the antifungal drugs available for successful treatment of drug-resistant biofilms are very few, and as such, new strategies need to be explored against them. The aim of this study was to evaluate the efficacy of phenylpropanoids of plant origin against planktonic cells, important virulence factors, and biofilm forms of C. albicans. Standard susceptibility testing protocol was used to evaluate the activities of 13 phenylpropanoids against planktonic growth. Their effects on adhesion and yeast-to-hyphae morphogenesis were studied in microplate-based methodologies. An in vitro biofilm model analyzed the phenylpropanoid-mediated prevention of biofilm development and mature biofilms using XTT-metabolic assay, crystal violet assay, and light microscopy. Six molecules exhibited fungistatic activity at ${\leq}0.5mg/ml$, of which four were fungicidal at low concentrations. Seven phenylpropanoids inhibited yeast-to-hyphae transition at low concentrations (0.031-0.5 mg/ml), whereas adhesion to the solid substrate was prevented in the range of 0.5-2 mg/ml. Treatment with ${\leq}0.5mg/ml$ concentrations of at least six small molecules resulted in significant (p < 0.05) inhibition of biofilm formation by C. albicans. Mature biofilms that are highly resistant to antifungal drugs were susceptible to low concentrations of 4 of the 13 molecules. This study revealed phenylpropanoids of plant origin as promising candidates to devise preventive strategies against drug-resistant biofilms of C. albicans.

• Mycobiology
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• 제29권1호
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• pp.19-26
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• 2001

Defense mechanisms against anthracnose disease caused by Colletotrichum orbiculare on the leaf surface of cucumber plants after pre-treatment with plant growth promoting rhizobacteria(PGPR), amino salicylic acid(ASA) or C. orbiculare were compared using a fluorescence microscope. Induced systemic resistance was mediated by the pre-inoculation in the root system with PGPR strain Bacillus amylolquefaciens EXTN-1 that showed direct antifungal activity to C. gloeosporioides and C. orbiculare. Also, systemic acquired resistance was triggered by the pre-treatments on the bottom leaves with amino salicylic acid or conidial suspension of C. orbiculare. The protection values on the leaves expressing SAR were higher compared to those expressing ISR. After pre-inoculation with PGPR strains no change of the plants was found in phenotype, while necrosis or hypersensitive reaction(HR) was observed on the leaves of plants pre-treated with ASA or the pathogen. After challenge inoculation, inhibition of fungal growth was observed on the leaves expressing both ISR and SAR. HR was frequently observed at the penetration sites of both resistance-expressing leaves. Appressorium formation was dramatically reduced on the leaves of plants pre-treated with ASA, whereas EXTN-1 did not suppress the appressorium formation. ASA also more strongly inhibited the conidial germination than EXTN-1. Conversely, EXTN-1 significantly increased the frequency of callose formation at the penetration sites, but ASA did not. The defense mechanisms induced by C. orbiculare were similar to those by ASA. Based on these results it is suggested that resistance mechanisms on the leaf surface was different between on the cucumber leaves expressing ISR and SAR, resulting in the different protection values.

• Mycobiology
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• 제42권1호
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• pp.52-58
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• 2014

A nucleoside diphosphate-linked moiety X (Nudix) hydrolase-like gene, YSA1, has been identified as one of the gromwell plant extract-responsive genes in Cryptococcus neoformans. Ysa1 is known to control intracellular concentrations of ADP-ribose or O-acetyl-ADP-ribose, and has diverse biological functions, including the response to oxidative stress in the ascomycete yeast, Saccharomyces cerevisiae. In this study, we characterized the role of YSA1 in the stress response and adaptation of the basidiomycete yeast, C. neoformans. We constructed three independent deletion mutants for YSA1, and analyzed their mutant phenotypes. We found that ysa1 mutants did not show increased sensitivity to reactive oxygen species-producing oxidative damage agents, such as hydrogen peroxide and menadione, but exhibited increased sensitivity to diamide, which is a thiol-specific oxidant. Ysa1 was dispensable for the response to most environmental stresses, such as genotoxic, osmotic, and endoplasmic reticulum stress. In conclusion, modulation of YSA1 may regulate the cellular response and adaptation of C. neoformans to certain oxidative stresses and contribute to the evolution of antifungal drug resistance.

• 한국미생물·생명공학회지
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• 제47권4호
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• pp.651-661
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• 2019

Targeting the pathogen viability using drugs is associated with development of drug resistance due to selective pressure. Hence, there is an increased interest in developing agents that target bacterial virulence. In this study, the inhibitory effect of ciclopirox, an antifungal agent with iron chelation potential, on the microbial virulence factors was evaluated in 26 clinical MDR Pseudomonas aeruginosa isolates collected from Alexandria Main University Hospital, a tertiary hospital in Egypt. Treatment with 9 ㎍/ml ciclopirox inhibited the hemolytic activity in 70% isolates, reduced pyocyanin production, decreased protease secretion in 46% isolates, lowered twitching and swarming motility, and decreased biofilm formation by 1.5- to 4.5-fold. The quantitative real-time PCR analysis revealed that treatment with ciclopirox downregulated the expression levels of alkaline protease (aprA) and pyocyanin (phzA1). Ciclopirox is used to treat hematological malignancies and the systemic administration of ciclopirox is reported to have adequate oral absorption with a satisfactory drug safety profile. It is important to calculate the appropriate clinical dose and therapeutic index to reposition ciclopirox from a topical antifungal agent to a promising virulence-modifying agent agent against P. aeruginosa, a problematic Gram-negative pathogen.

• KSBB Journal
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• 제32권2호
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• pp.146-152
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• 2017

Vulvovaginal candidiasis (VVC) is one of the urogenital infections occurring in women worldwide. Candida albicans is generally observed among various types of microorganisms causing VVC. Antibiotic therapy is typical, and the use of Lactobacilli probiotics is to be recognized as a promising alternative. The aim of this study was to select vaginal lactobacilli with probiotic properties against C. albicans. In a previous study, we isolated 38 lactobacilli from vagina of Korean women and 20 isolates were shown to inhibit C. albicans. We further selected 10 isolates which were able to inhibit C. albicans less than $10^5CFU/mL$. Among these selected strains, Lactobacillus salivarius MG242 (identified by 16s rRNA sequencing) was finally selected based on its strong anti-candidal activity, acid/bile salt resistance and adhesion property. Indirect adhesion activity of MG242 measured by auto-aggregation assay showed more than 60% auto-aggregation after 5 h standing. Taken these results together, the selected strain MG242 may have potential for application in vagina health related products.

• The Plant Pathology Journal
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• 제19권1호
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• pp.51-56
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• 2003

Rehmannia glutinosa is one of the most important medicinal crops in Korea. However, various plant pathogens, including Fusatium spp., cause great damage on R. glutinosa and result in enormous economic losses. This study was conducted to breed Fusarium-resistant plants by using Agrobacterium tumefaciences and AFP (anti-fungal protein) gene. The plant material used was a native accession of R. glutinosa. The PCR analysis was conducted to verify transgenicity. Based on the PCR analysis, nptII band was observed in transgenic plant genome. Southern blot and AFP protein analyses also showed the expression of this gene in transgenic plants. Expression of AFP in transgenic plants offers the possibility of developing resistance to fungal infection.

• 동의생리병리학회지
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• 제26권1호
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• pp.74-80
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• 2012

Candida albicans is a common opportunistic pathogen and is frequently associated with biofilm formation occurring on the surfaces of host tissues and medical devices. On account of the distinct resistance of C. albicans biofilms to the conventional antifungal agents, new strategies are required to cope with these infections. The root of Polygonum cuspidatum has been used for medicinal purposes in East Asia. The aim of this study was to assess the anticandidal potential of the P. cuspidatum ethanol extract by evaluating biofilm formation, integrity of the cell membranes of C. albicans and adhesion of C. albicans cells to polystyrene surfaces. The growth and development of the biofilm was assessed using an XTT reduction assay, and the extract (0.39 mg/ml) significantly reduced ($41.1{\pm}17.8%$) biofilm formation of 11 C. albicans strains. The extract damaged the cell membranes of C. albicans and remarkably inhibited cell adhesion to polystyrene surfaces. The plant extract displayed fungistatic activity without significant hemolytic activity. Based on the results of this study, the P. cuspidatum extract has promising potential for use in treating biofilm-associated Candida infection.

• 미생물학회지
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• 제47권4호
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• pp.295-301
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• 2011

아쿠아포린(aquaporin)은 MIP (Major Intrinsic Protein) 패밀리에 속하는 물 수송 채널(water transport channel) 단백질로 단세포 생물인 박테리아부터 다세포 고등생물인 인간에 이르기까지 다양한 기관계에서 잘 보존되어 있다. 아쿠아포린은 정통아쿠아포린(orthodox aquaporin)과 아쿠아글리세로포린(aquaglyceroporin)으로 구분되는데, 정통아쿠아포린은 주로 세포내의 물 유입 및 수송에 관여하며 아쿠아글리세로포린은 glycerol, polyol, urea를 비롯한 작은 비극성 분자의 수송에 관여하는 것으로 알려져 있다. 최근까지 효모에서 아쿠아포린 기능이 일부 밝혀졌지만 Aspergillus 속을 포함하는 사상성 진균에서는 거의 연구가 되어있지 않은 실정이다. 본 연구에서는 A. nidulans의 유전체 염기서열 정보를 분석하여 하나의 정통아쿠아포린(aqpA)과 네 개의 아쿠아글리세로포린(aqpB-E)을 발견하였다. 이를 바탕으로 aqpA 유전자 결실돌연변이들을 만들어 그 기능을 분석하였다. aqpA 결실돌연변이는 각종 삼투 스트레스(osmotic stress)에서는 표현형의 변화가 거의 관찰되지 않았으며 이는 이들 유전자가 삼투 스트레스에 반응하지 않거나 유전자의 중복성 때문으로 여겨진다. 그러나 항진균제인 fluconazol에 대해서 그 감수성이 적어지는 것이 관찰 되었다. 이는 aqpA 유전자가 삼투스트레스 반응보다 항진균제의 감지에 더 기능을 가지고 있을 수 있음을 시사한다.

• 생명과학회지
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• 제25권8호
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• pp.910-916
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• 2015

최근 식물 성장에 있어 곰팡이 독소에 관련된 질병에 효과가 있는 Bacillus mojavensis 균주 사용의 보고가 있다. 우리는 B. mojavensis KJS-3균주의 다양한 온도, 염도, 에탄올, pH에서 성장하는 특징을 확인 하였다. B. mojavensis KJS-3균주는 Polymerase chain reaction 분석에 의해 fengycin을 LC-MS/MS 분석을 통해서는 iturin 및 surfactin 와 같은 cyclic lipopeptides를 생산함을 확인 하였다. B. mojavensis KJS-3균주는 식물 유해 곰팡이 균주인 Botrytis cinerea, Rhizoctonia solani AG-4, Sclerotinia sclerotiorum, Colletotricum goeosporioides에 항곰팡이 효과가 있음을 확인하였고 이 결과를 바탕으로 인삼재배에 있어 B. mojavensis KJS-3를 사용하여 성장을 관찰한 결과 뿌리 내에서 성장하여 plant growth promoting endophyte가 있음을 알 수 있었다. 이러한 특징들에 의해 미생물 농약 및 비료로 사용할 수 있을 것이다.