• Journal of Applied Biological Chemistry
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• v.42 no.3
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• pp.146-150
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• 1999

As a part of the integrated disease system in greenhouse, an antifungal fungus(AF1) was isolated from greenhouse soil. It exhibited strong inhibitory activites against Pythium ultimum, Phytophtora capsici, Rhizoctonia solani, Botrytis cinerea, and Fusarium oxysporum based on dual culture on 1/5 strength of potato dextrose agar between antagonistic fungus and several plant pathogens. The antagonistic fungus was identified as Chaetomium cochliodes, based on morphological characteristics; the body of the perithecium bears straight or slightly wavy, unbranched hairs, whilst the apex bears a group of spirally coiled hairs. To investigate antagonistic principles, antifungal compound was extracted and fractionated by different solvent systems. An antifungal compound was isolated as pure crystal from is culture filtrate using organic solvent extraction and column chromatography, followed by preparative thin layer chromatography. The chemical structure of the purified antifungal compound was identified as chaetoglobosin A based on the data obtained form $^1H-NMR$, $^{13}C-NMR$, DEPT 90, 135, $^1H-^1H$ COSY, $^1H-^{13}C$ COSY and EI/MS. $ED_{50}$ values of the chaetoglobosin A against P. ultimum, P. capsici, R. solani, B. cinerea and F. oxysporum were 1.98, 4.01, 4.16, 2.67 and 35.14 ppm, respectively.

• Journal of Microbiology and Biotechnology
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• v.19 no.12
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• pp.1688-1694
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• 2009

A novel strain of fluorescent pseudomonad (PB-St2) was isolated from surface-sterilized stems of sugarcane grown in Pakistan. The bacterium was identified as Pseudomonas aurantiaca on the basis of 16S rRNA gene sequence analysis and results from physiological and biochemical characteristics carried out with API50 CH and QTS 24 bacterial identification kits. Assays using substrate-specific media for enzymes revealed lipase and protease activities but cellulase, chitinase, or pectinase were not detected. The bacterium was unable to solubilize phosphate or produce indole acetic acid. However, it did produce HCN, siderophores, and homoserine lactones. In dual culture assays on agar, the bacterium showed antifungal activity against an important pathogen of sugarcane in Pakistan, namely Colletotrichum falcatum, as well as for pathogenic isolates of Fusarium oxysporium and F. lateritium but not against F. solani. The antifungal metabolites were identified using thin-layer chromatography, UV spectra, and MALDI-TOFF spectra and shown to be phenazine-1-carboxylic acid (PCA), 2-hydroxyphenazine (2-OH-PHZ), and N-hexanoyl homoserine lactone (HHL) (assessed using only TLC data). The capacity of this bacterium to produce HCN and 2-OH-PHZ, as well as to inhibit the growth of C. falcatum, has not been previously reported.

• Mycobiology
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• v.42 no.2
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• pp.206-209
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• 2014

In this study, we identified the causative agent of stem-end rot in potatoes that were grown in Gangwon alpine areas of Korea in 2013. The disease symptoms included appearance of slightly sunken circular lesion with corky rot on the potato surface at the stem-end portion. The fungal species isolated from the infected potatoes were grown on potato dextrose agar and produced white aerial mycelia with dark violet pigments. The conidiophores were branched and monophialidic. The microconidia had ellipsoidal to cylindrical shapes and ranged from $2.6{\sim}11.4{\times}1.9{\sim}3.5{\mu}m$ in size. The macroconidia ranged from $12.7{\sim}24.7{\times}2.7{\sim}3.6{\mu}m$ in size and had slightly curved or fusiform shape with 2 to 5 septate. Chlamydospores ranged from $6.1{\sim}8.1{\times}5.7{\sim}8.3{\mu}m$ in size and were present singly or in pairs. The causal agent of potato stem-end rot was identified as Fusarium oxysporum by morphological characterization and by sequencing the internal transcribed spacer (ITS1 and ITS4) regions of rRNA. Artificial inoculation of the pathogen resulted in development of disease symptoms and the re-isolated pathogen showed characteristics of F. oxysporum. To the best of our knowledge, this is the first study to report that potato stem-end rot is caused by F. oxysporum in Korea.

• Mycobiology
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• v.42 no.4
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• pp.368-375
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• 2014

Red ginseng (Panax ginseng), a Korean traditional medicinal plant, contains a variety of ginsenosides as major functional components. It is necessary to remove sugar moieties from the major ginsenosides, which have a lower absorption rate into the intestine, to obtain the aglycone form. To screen for microorganisms showing bioconversion activity for ginsenosides from red ginseng, 50 yeast strains were isolated from Korean traditional meju (a starter culture made with soybean and wheat flour for the fermentation of soybean paste). Twenty strains in which a black zone formed around the colony on esculin-yeast malt agar plates were screened first, and among them 5 strains having high ${\beta}$-glucosidase activity on p-nitrophenyl-${\beta}$-D-glucopyranoside as a substrate were then selected. Strain JNO301 was finally chosen as a bioconverting strain in this study on the basis of its high bioconversion activity for red ginseng extract as determined by thin-layer chromatography (TLC) analysis. The selected bioconversion strain was identified as Candida allociferrii JNO301 based on the nucleotide sequence analysis of the 18S rRNA gene. The optimum temperature and pH for the cell growth were $20{\sim}30^{\circ}C$ and pH 5~8, respectively. TLC analysis confirmed that C. allociferrii JNO301 converted ginsenoside Rb1 into Rd and then into F2, Rb2 into compound O, Rc into compound Mc1, and Rf into Rh1. Quantitative analysis using high-performance liquid chromatography showed that bioconversion of red ginseng extract resulted in an increase of 2.73, 3.32, 33.87, 16, and 5.48 fold in the concentration of Rd, F2, compound O, compound Mc1, and Rh1, respectively.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.960-966
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• 2012

The diversity and composition of yeast populations may greatly impact wine quality. This study investigated the yeast microbiota in two different types of wine fermentations: direct inoculation of a commercial starter versus pied de cuve method at an industrial scale. The pied de cuve fermentation entailed growth of the commercial inoculum used in the direct inoculation fermentation for further inoculation of additional fermentations. Yeast isolates were collected from different stages of wine fermentation and identified to the species level using Wallersterin Laboratory nutrient (WLN) agar followed by analysis of the 26S rDNA D1/D2 domain. Genetic characteristics of the Saccharomyces cerevisiae strains were assessed by a rapid PCR-based method, relying on the amplification of interdelta sequences. A total of 412 yeast colonies were obtained from all fermentations and eight different WL morphotypes were observed. Non-Saccharomyces yeast mainly appeared in the grape must and at the early stages of wine fermentation. S. cerevisiae was the dominant yeast species using both fermentation techniques. Seven distinguishing interdelta sequence patterns were found among S. cerevisiae strains, and the inoculated commercial starter, AWRI 796, dominated all stages in both direct inoculation and pied de cuve fermentations. This study revealed that S. cerevisiae was the dominant species and an inoculated starter could dominate fermentations with the pied de cuve method under controlled conditions.

• The Korean Journal of Mycology
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• v.16 no.2
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• pp.70-78
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• 1988

To obtain basic information for the genetic analysis and breeding of Flammulina velutipes, some factors affecting the release of protoplasts from the fungus were studied. Potato Dextrose peptone Agar medium was suitable for the growth of the mycelium and the protoplast formation of F. velutipes. The culture age for the high yields of protoplast was 5 days on PDPA. Few protoplasts were formed from the mycelium cultured on Mushroom minimum Media. The highest yield of protoplasts was obtained in enzyme solution containing Novozyme 234 plus cellulase CP at 10 mg $ml^{-1}$ concentration, while a half amount of protoplasts was obtained in enzyme solution containing Novozyme 234 only. The optimal reaction time of the mycelium in the Iytic enzyme mixtures was 3 hours. The best osmotic stabilizer for the protoplast formation of the mycelium was 0.6M sucrose without buffer at pH 6.2.

• The Journal of the Korean Society for Microbiology
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• v.22 no.1
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• pp.35-53
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• 1987

Multiply resistant Shigella strains isolated in Taegu area were subjected for the characterization of R plasmids. All strains isolated in 1984 and 1985 were susceptible to gentamicin, amikacin, and cephalothin, and most strains were susceptible to kanamycin (Km) and rifampin by agar dilution antimicrobial susceptibility test. The resistance frequency of S. flexneri against ampicillin (Ap) was higher than that of S. sonnei. The strains resistant to sulfisomidine (Su) and trimethoprim (Tp) were found at higher frequency in S. sonnei than in S. flexneri. The most prevalent resistance pattern of S. flexneri was chloramphenicol (Cm) tetracycline (Tc) streptomycin (Sm) Ap, followed by the pattern of CmTcSmSuApTp, CmTcSmSuApTp nalidixic acid, and CmTcSmSuAp in the decreasing order. The antibiogram of CmTcSmSuTp was found to be the most frequent pattern in S. sonnei. The ratio of conjugal transfer of S. flexneri was 47% and 75% of S. sonnei. The average number of plasmid harboring in Shigella was 4 and the size of plasmid ranged 1.3 to 134 megadalton (Mdal). Most S. flexneri carried plasmids of 2 to 3 Mdal and S. sonnei carried those of 3 to 4 Mdal size. The sizes of conjugative plasmids ranged 40-90 Mdal. The incompatibility group (Inc) F II plasmids (54-59 Mdal) were most frequent and rare Inc B plasmids (60 Mdal) of isolates in 1979 and 1980 and Inc FI (87 Mdal) of 1983 isolates were able to be classified by the colony test with standard reference plasmids. The R plasmids of known Inc group were tested for the restriction endonuclease analysis. The pattern of plasmids digested by EcoRl were apparently different by the Inc group but there was no significant difference between species or by the resistance patterns. Nonconjugative plasmids and their phenotypes were identified by transformation test. The transformants were resistant to less than two drugs. Colicin producing transformants carried the Col plasmid of 3.7 or 3.9 Mdal size. $Ap^r$ plasmids derived from S. sonnei were found to be mobilized by transfer factor RT641 to E. coli #CS100. $Ap^r$ plasm ids of same size shared by S. flexneri, S. sonnei, and E. coli were digested with Pstl. All of them showed two restriction fragments of 2.8 kilobase(kb) and 0.7kb. Other plasmids ($Sm^r\;Su^r$) derived from S. flexneri, S. boydii, and S. sonnei were digested with Pstl and they showed same restriction fragment patterns of 3.1kb and 2.9kb. The plasmid profiles of three strains of S. sonnei producing colicin and showing same resistance pattern of CmTcSmSuApTpKm appeared to be similar. Restriction patterns by EcoRl and the behavior of plasmids in conjugation or transformation process were also similar between those plasmids. The restriction patterns were significantly different between the plasmids of Inc FI group and those of unclassified Inc group.

• Microbiology and Biotechnology Letters
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• v.38 no.3
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• pp.295-301
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• 2010

Sheath rot and dry rot disease caused by Pseudomonas marginalis and Fusarium oxysporum were serious problems in garlic farmland. In this study, total of 160 indigenous antagonistic bacteria were isolated from 16 farmlands in Yeongcheon, Korea. Among these, 15 strains were able to inhibited P. marginalis and F. oxysporum. The 16s rDNA genes of the selected 15 strains were amplified and sequenced. The strains has strong antagonistic ability against garlic pathogens was achieved Bacillus subtilis YC82, B. vallismortis YC84, B. amyloliquefaciens YC240. The selected 3 strains tested for investigation of antifungal mechanisms further analyses; 3 strains of these validated for production of siderophore, ${\beta}$-glucanase and chitinase using CAS (chrome azurol S) blue agar, CMC-congo red agar and DNS method. The 3 strains were able to utilized insoluble phosphate as dertermined by vanado-molybdate method. The 3 strains verified for production of auxin and gibberellic acid using Salkowski test and holdbrook test. Also, 3 strains showed stimulation germination, stem growth promoting activity on the in vivo test. The 3 strains were able to effectively suppress P. marginalis and F. oxysporum causing sheath rot and dry rot diseases on the in vivo pot test.

• Korean journal of applied entomology
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• v.23 no.3 s.60
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• pp.142-146
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• 1984

Soils suppressive and conducive to ginseng root rot were studied by examining the mycelial growth of Fusarium solani, Phytophthora cactorum, and Sclerotinia sp. on extracts of each type soil. Rhizosphere environments of the two soils were also compared. Mycelial growth of all root rot fungi used was more severely restrained on the suppressive soil extract agar than that of conducive one. However, when heated at 100C for 30 minutes, mycelial growth of F. solani and Sclerotinia sp. was not affected, regardless of type soil used, whereas R. solani and P. cactorum grew better on conducive soil extract. Mycelial growth of all fungi used was stimulated as the treated temperature became higher. No significant differences between the two types of the soil were found in propagules of F. solani. The numbers of total fungi and total bacteria and the ratioes of total fungi to Fusarium and total bacteria to Fusarium were higher in the suppressive soils than in the conducive ones. Higher amount of clay existed in the suppressive soils, Mg and Na contents were lower in those soils than the conducive ones.

• Journal of Microbiology and Biotechnology
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• v.32 no.12
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• pp.1537-1546
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• 2022

Staphylococcus aureus is a cause of high mortality in humans and therefore it is necessary to prevent its transmission and reduce infections. Our goals in this research were to investigate the frequency of methicillin-resistant S. aureus (MRSA) in Taif, Saudi Arabia, and assess the relationship between the phenotypic antimicrobial sensitivity patterns and the genes responsible for resistance. In addition, we examined the antimicrobial efficiency and application of silver nanoparticles (AgNPs) against MRSA isolates. Seventy-two nasal swabs were taken from patients; MRSA was cultivated on Mannitol Salt Agar supplemented with methicillin, and 16S rRNA sequencing was conducted in addition to morphological and biochemical identification. Specific resistance genes such as ermAC, aacA-aphD, tetKM, vatABC and mecA were PCR-amplified and resistance plasmids were also investigated. The MRSA incidence was ~49 % among the 72 S. aureus isolates and all MRSA strains were resistant to oxacillin, penicillin, and cefoxitin. However, vancomycin, linezolid, teicoplanin, mupirocin, and rifampicin were effective against 100% of MRSA strains. About 61% of MRSA strains exhibited multidrug resistance and were resistant to 3-12 antimicrobial medications (MDR). Methicillin resistance gene mecA was presented in all MDR-MRSA strains. Most MDR-MRSA contained a plasmid of > 10 kb. To overcome bacterial resistance, AgNPs were applied and displayed high antimicrobial activity and synergistic effect with penicillin. Our findings may help establish programs to control bacterial spread in communities as AgNPs appeared to exert a synergistic effect with penicillin to control bacterial resistance.