• Journal of Microbiology and Biotechnology
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• v.27 no.5
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• pp.1010-1022
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• 2017

Hybrid histidine kinase is part of a two-component system that is required for various stress responses and pathogenesis of pathogenic fungi. The Tco1 gene in human pathogen Cryptococcus neoformans encodes a hybrid histidine kinase and is important for pathogenesis. In this study, we identified a Tco1 homolog, UmTco1, in the maize pathogen Ustilago maydis by bioinformatics analysis. To explore the role of UmTco1 in the survival of U. maydis under environmental stresses and its pathogenesis, ${\Delta}umtco1$ mutants were constructed by allelic exchange. The growth of ${\Delta}umtco1$ mutants was significantly impaired when they were cultured under hyperosmotic stress. The ${\Delta}umtco1$ mutants exhibited increased resistance to antifungal agent fludioxonil. In particular, the ${\Delta}umtco1$ mutants were unable to produce cytokinesis or conjugation tubes, and to develop fuzzy filaments, resulting in impaired mating between compatible strains. The expression levels of Prf1, Pra1, and Mfa1, which are involved in the pheromone pathway, were significantly decreased in the ${\Delta}umtco1$ mutants. In inoculation tests to the host plant, the ${\Delta}umtco1$ mutants showed significantly reduced ability in the production of anthocyanin pigments and tumor development on maize leaves. Overall, the combined results indicated that UmTco1 plays important roles in the survival under hyperosmotic stress, and contributes to cytokinesis, sexual development, and virulence of U. maydis by regulating the expression of the genes involved in the pheromone pathway.

• Journal of Life Science
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• v.15 no.2 s.69
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• pp.279-286
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• 2005

The Opuntia ficus-indica var. saboten Makino (Cactus) is a tropical or subtropical plant, which is cultivated or grows naturally in Jeju island. It has been widely used as folk medicine for burned wound, edema and indigestion. In addition, its extract has been claimed to have several biological activities including anti-inflammation in oriental medicine. In this study, we examined the antimicrobial activities of the methanol extract of Opuntia ficus-indica var. saboten Makino. The extract showed a broad spectrum of antimicrobial activity against pathogenic bacteria, including antibiotics resistant bacteria (MRSA, R-P. aeruginosa, VRE) and Propionibacterium acnes, yeast, and fungi. The extract retained the activity after heat treatment for 15 min at $100^{\circ}C$ and $121^{\circ}C$ and after extended storage, up to 10 weeks storage period at $4^{\circ}C$ and $25^{\circ}C$, also stably retained its activity. It showed a better inhibitoring effect to the growth of E. coli than sodium benzoate did it at the same concentration. Addition of various salts or metal ions did not affect on its antimicrobial activity. Therefore, the antimicrobial characteristics of the extract can be applicable as a natural preservative and an antimicrobial agent for bacterial disease.

• Journal of Life Science
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• v.9 no.1
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• pp.8-14
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• 1999

The growth rate of the A252 strain was increased in tryptic soy broth (TSB) and malt extract-yeast extract medium (ISP-2), but the antifungal activity of culture filtrate was efficient in the media of TSB and nutrient broth. The mycelial growth and the antifungal activity of culture filtrate in TSB medium were optimized at $25^{\circ}C$ and pH 6.5. The growth in 2$\%$TSB concentration was more effective than 1$\%$, but there was no difference of the antifungal activity by the TSB concentrations. The mycelial growth of A252 strain reached to maximum at 72 hr after inoculation, whereas the antifungal activity of culture filtrate was shown to have the highest level at idiophase (60 hr) after inoculation and was decreased a little after 96 hr incubation. The antifungal activity was stable in the pH range of 4 to 11 and evenly at $121^{\circ}C$. The A252 strain was characterized as Streptomyces species by the physiological properties and examination of sporophore me morphology.

• The Korean Journal of Mycology
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• v.40 no.4
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• pp.258-265
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• 2012

Bacterial strains isolated from diseased red pepper fruits showed inhibitory effect on mycelial growth and spore germination of Colletotrichum gloeosporioides. The bacterium was identified as Paenibacillus sp. based on its physiological, biochemical characteristics and MicroLog analysis and named Paenibacillus sp. IUB225-08. The bacterium showed the highest level of antifungal activity C. gloeosporioides when cultured at $25^{\circ}C$ for 60 hrs in LB broth with initial pH of 7.0. The butanol fraction from culture extract of Paenibacillus sp. IUB225-08 effectively inhibited the mycelial growth and spore germination of C. gloeosporioides than any other agricultural chemicals tested. Pepper fruits and seeds treated with spores of C. gloeosporioides showed symptoms, while those treated with the culture extract and C. gloeosporioides together did not show any symptoms. Therefore, the culture extract of Paenibacillus sp. IUB225-08 have a potential for biocontrol agent of red pepper anthracnose.

• Korean Journal of Microbiology
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• v.37 no.4
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• pp.305-311
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• 2001

Antifungal bacterium, Bacillus subtilis YS1 was isolated from Yusong hot spring showed broad antifungal spectrum against 12 kinds of plant pathogenic fungi and Candida albicans, animal pathogen. From the gamma($Co^{60}$) radiation sensitivity test, $D_10$ value was 2.08 kGy and it survived above 20 kGy of radiation dose. Several mutants were induced by gamma radiation. Among them, YS1-1009 mutant showed resistance against tebuconazole of herbicide, increased activity against Botryoshaeria dothidea and ligninase activity. YS67 mutant was antifungal deficient auxotrophic mutants(trp-pro-or arg-ura-). From this results, it suggested that gamma irradiation could be useful method for mutant induction.

• Korean Journal of Microbiology
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• v.44 no.3
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• pp.258-263
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• 2008

Late blight, one of the most important disease in many agricultural crops, is caused by Phytophthora infestans. Fusarium wilt is a vascular disease of many plants caused by Fusarium oxysporum. Some bacteria isolated from rhizosphere were screened for their ability to inhibit the growth of F. oxysporum and P. infestans. Productions of siderophore, $\beta-1$,3-glucanase, hydrogen cyanide and chitinase by 4 isolated strains were examined. Among them, Bacillus sp. RFO41 most effectively inhibited the growth of F. oxysporum. The highest productions of siderophore and $\beta-l$,3-glucanase were shown in the culture of Bacillus sp. RFO41. Bacillus strain PS2 was most effective against P. infestans. PS2 showed the highest production of chitinase and hydrogen cyanide. A significant relationship was shown between the antagonistic effects of isolates against F. oxysporum and P. infestans and their production level of siderophore, $\beta-1$,3-glucanase, hydrogen cyanide, and chitinase.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.296-304
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• 1994

Antibiotic substances were produced by Bacillus subtilis YB-70, a potential biocontrol agent found to suppress root-rot of eggplant (Solanum melonggena L) caused by Fusarium solani, in a dextrose glutamate medium and isolated by isoelectric precipitation. Partial purification was performed by column chromatography on silica gel with two solvent systems: chloroform-methanol and methanol-chloroform-water as eluting solvents, This active fraction YBS-1 s contained antifungal activity were soluble in ethanol, methanol, and water, but were not soluble in other solvents including acetone, butanol, ethyl ether, dimethylformamide, propanol, and etc. High performance liquid chromatography and thin layer chromatographic separation of YBS-1s showed that they have been composed of three biological active bands that were named YBS-1A, -1B, and -1C. The substances were stable to heat and resistant to protease. YBS-1s were active against a wide range of plant pathogenic fungi but did not inhibit the growth of bacteria and yeasts. They were not only fungicidal but also fungistatic against chlamydospores of F. solani. The $ED_{50}$ values for the chlamydospore germination and the germ-tube growth of F. solani were $O.725\mu\textrm{m}/ml\;and\;O.562\mu\textrm{m}/ml$, respectively. Microscopic observations proved the substances restricted the growth of phytopathogenic fungus F. solani by spore burst followed by dissolving of its germ-tube, and caused abnormal hyphal swelling after application to chlamydospores or growing hyphae. Cultural filtrate of B; subtilis YB-70 also suppressed the development of root-rot of eggplant in pot tests.

• Journal of Life Science
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• v.16 no.6
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• pp.994-1000
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• 2006

Stevia rebaudiana Bertoni is a sweet herb of the Asteraceae family originally derived from South America. Twenty three bacterial strains and ten yeast strains were isolated from fermented Stevia extract and identified by general taxonomic methods and molecular genetic method. Isolated strains from fermented Stevia extract include ten species of bacteria which belong to five genus and one species of yeast. Based on 16S and 18S rDNA sequence analysis, phylogenetic trees were constructed. Antimicrobial activity of the isolated strains was examined against various bacteria and plant-pathogenic fungi. Among them, Lactobacillus paracasei SB13 showed strong antibacterial activity towards a wide range of bacteria. These results may be useful to develop environmentally friendly microbial agent for soil improvement.

• Korean Journal of Medicinal Crop Science
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• v.26 no.4
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• pp.302-307
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• 2018

Background: A soil-borne pathogenic fungus, Ilyonectria radicicola (Cylindrocarpon destructans) causes root rot on ginseng (Panax ginseng C. A. Meyer) and is known to attack many other plants. The Nectria/Neonectria radicicola complex has been renamed as the I. radicicola complex after analysis of its multi-gene relatedness and morphological characteristics. The fungi in this complex have been reclassified into 16 species under the genus Ilyonectria based on characteristics analysis Methods and Results: To obtain useful data from the Korean ginseng root rot, I. radicicola was isolated from the rhizosphere soils of the chestnut tree. They were identified through a pathogenicity test and a survey of the morphological features. The existence of I. radicicola in soil samples was confirmed by PCR detections using nested PCR with species-specific primer sets. These were subsequenctly isolated on semi-selective media from PCR-positive soils. Genetic analysis of the I. radicicola complex containing these pathogens was done by comparing the DNA sequences of the histone h3 region. These isolates originating from the rhizosphere soils of chestnut constituted a clade with other closely related species or I. radicicola isolates originating from ginseng or other host plants, respectively. Additionally, the pathogenicity tests to analyze the characteristics of these I. radicicola isolates revealed that they caused weakly virulent root rot on ginseng. Conclusions: This is the first study reporting that I. radicicola isolates from chestnut rhizosphere soils can attack ginseng plant in Korea. Thus, these results are expected to provide informations in the selection of suitable fields for ginseng cultivation.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.309-312
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• 2013

Fungal cell walls consist of various glucans and chitin. Fungi produce chitinases for their growth and development. The inky cap, Coprinellus congregatus, produces at least two different chitinases during its life cycle. Chitinase 1 (chi1) is expresses throughout its life cycle while chitinase 2 (chi2) is expressed at the mushroom autolysing phase. The cloned cDNA of chi1 is successfully expressed as a fusion protein with c-myc in Pichia pastoris, and purified by the affinity chromatography. The optimum pH and temperature of Chi1 was pH 8.0 and $35^{\circ}C$, respectively when 4-nitrophenyl N,N',N"-triacetyl-${\beta}$-D-chitotrioside was used as the substrate. The $K_m$ value and $V_{max}$ for the substrate was 0.780 mM and 0.10 OD $min^{-1}unit^{-1}$, respectively. The addition of purified Chi1 resulted in total growth inhibition against several plant pathogenic fungi such as Alternaria alternata, Fusarium graminearum and Trichoderma harzianum at the concentration of 60 ${\mu}g/ml$.