• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1787-1795
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• 2015

The transition from primary to secondary metabolism in antibiotic-producing Streptomyces correlates with expression of genes involved in stress responses. Consequently, regulatory pathways that regulate specific stress responses are potential targets to manipulate to increase antibiotic titers. In this study, genes encoding key proteins involved in regulation of the osmotic stress response in Streptomyces avermitilis, the industrial producer of avermectins, are investigated as targets. Disruption of either osaB_Sa, encoding a response regulator protein, or osaC_Sa, encoding a multidomain regulator of the alternative sigma factor SigB, led to increased production of both oligomycin, by up to 200%, and avermectin, by up to 37%. The mutations also conditionally affected morphological development; under osmotic stress, the mutants were unable to erect an aerial mycelium. In addition, we demonstrate the delivery of DNA into a streptomycete using biolistics. The data reveal that information on stress regulatory responses can be integrated in rational strain improvement to improve yields of bioactive secondary metabolites.

• Korean Journal of Agricultural Science
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• v.17 no.2
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• pp.77-81
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• 1990

Effects of buprofezin, an inhibitor of chitin synthesis, on mycelial growth, protoplast formation and reversion of Pleurotus ostreatus and P. sajor-caju were investigated. The mycelial growth of Pleurotus ostreatus and P. sajor-caju was the inhibited by buprofezin treatment, and the inhibition rate was severer as the concentration of the buprofezin increased. Aerial mycelium formation was increased by buprofezin treatment, but mycelial morphology was not changed. Protoplast formation of Pleurotus ostreatus and P. sajor-caju. was significantly increased when buprofezin was added to the culture medium at the concentration of 200~500 ppm and the protoplast reversion of the mushrooms was also increased by the treatment of the buprofezin.

• Korean journal of applied entomology
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• v.20 no.1 s.46
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• pp.21-24
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• 1981

This study was conducted to obtain a supply of conidia sufficient for screening mungbean mutant lines for a source of resistance to Cercospora leaf spot caused by Cercospora canescens Ellis and Martin. Abundant sporulation occurred in cultures on mungbean leaf decoction oatmeal agar(MOA) exposed to about 2,500 Lux of fluorescent light. but it did not occur in continuous darkness. The conditions that produced maximum number of conidia was not coincided with those for vegetative growth and pigmentation in culture medium. Removal of aerial mycelium in culture by brushing with sterile water so enhanced the conidial production that oatmeal agar medium(OA) could be useful for production of abundant conidia by the treatment.

• The Plant Pathology Journal
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• v.18 no.3
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• pp.161-164
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• 2002

Colletotrichum musae was isolated from dark-brown anthracnose lesions on commercial banana (Musa sapientum L.) to establish the causal agent of the symptom. The fungus grew fast and produced white aerial mycelium on PDA. Acervuli developed abundantly on culture plates after incubation for 10 days at $25^{\circ}C$. Pinkish conidial masses were produced on the acervuli, which mostly coalesced together, Conidia were aseptate, hyaline, straight, ellipsoid to globose, and 14.5$\times$6.9 $\mu\textrm{m}$ in size. Black, clavate, round, or irregular-shaped appressoria measuring 8.8$\times$6.8 $\mu\textrm{m}$ were readily formed from germ tubes. Setae-like structures were not found either on the lesion or on the cultures. Sclerotia were also absent. Among the media, PDA medium was the best for mycelial growth. The optimum temperature for mycelial growth was $28^{\circ}C$, while the optimum pH ranged from pH 5.5 to 6.5. The isolates of C musae caused black necrotic lesions on banana fruits by needle-wound inoculation, and orange-colored spore masses were produced on the lesions. The fungus also caused discoloration on apple fruits inoculated.

• Korean Journal of Microbiology
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• v.46 no.3
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• pp.262-269
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• 2010

To investigate a quantitative evaluation of the actinobacteria, we have collected samples from various kinds of bamboo forest soil. Each different layers contained $2.7{\times}10^6-2.7{\times}10^8$ CFU/g of actinobacteria which was the highest in litter layers of Sasa boreali forest soil. We obtained 330 actinobacteria from different layers of bamboo forest soil; litter (100 strains), humus (70 strains), and rhizosphere soil (160 strains). Based on the colony morphology (aerial mycelium, substrate mycelium, and soluble pigment), isolates were divided into thirty-six groups and we selected 50 representative isolates. 16S rRNA gene sequence analysis showed Streptomyces was major actinobacteria (94%) and they were categorized as cluster I (2 strains), II (35 strains), III (6 strains), and IV (7 strains), respectively. The diversity index of 50 Streptomyces collected from the bamboo forest soil was calculated with the Shannon-Wiener method. Bamboo litter showed higher diversity index level of 3.33 than that of humus and rhizosphere soil. Also, antibiotic activities of our isolates were investigated against Botrytis cinerea, Xanthomonas campestris, Xanthomonas axonopodis pv. vesicatoria, and Bacillus cereus and found in 74, 16, 25, and 24 strains, respectively.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.397-403
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• 2009

For the research of the natural antioxidant from marine sources, an antioxidant-producing marine actinomycetes was isolated from sea water in Jeju coastal area. The strain was identified based on 16S rDNA sequencing, the morphology by a method of scanning electron microscopy, physiological and biochemical characteristics and cellular fatty acid analysis. The isolated strain ACT-1 cell size was $0.5\sim1.0{\mu}m$ and gram positive, aerobic, nonmotile, substrate mycelium are red and gray aerial mycelium. 16S rRNA sequence analysis showed that were Gram-positive bacteria grouped on Streptomyces genus. Results of cellular fatty acid analysis showed that major cellular fatty acids were $C_{15:0}$ anteiso (39.33%), $C_{16:1}$ cis 9 (11.96%), $C_{16:0}$ (13.08%) and $C_{17:0}$ anteiso (10.99%). Finally, strain was identified Streptomyces sp. ACT-1. The antioxidant activity of methanol extract from Streptomyces sp. ACT-1 was evaluated by measuring DPPH, hydroxyl, and alkyl radical scavenging activity using an electron spin resonance (ESR) spectrometer. DPPH radical scavenging activity of SBME-1 (Streptomyces broth methanol extract) was 67% at $1,000{\mu}g$/ml. Hydroxyl radical scavenging activity of SBME-1 was 84% at $500{\mu}g$/ml. Alkyl radical scavenging activity of SBME-1 was 71% at $1,000{\mu}g$/ml.

• Journal of Applied Biological Chemistry
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• v.60 no.2
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• pp.149-153
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• 2017

Contamination and growth of Trichoderma, a green mold, on the oak log and wooden chip or sawdust media can severely inhibit the growth of oak mushroom. Chemicals including pesticides and antibiotics are generally not allowed for the control of green mold disease during mushroom cultivation. In this study, bacterial pathogens causing blotch disease on the oyster mushrooms were isolated and their peptide toxins were purified for the control of green mold disease. Strains of Pseudomonas tolaasii secret various peptide toxins, tolaasin and its structural analogues, having antifungal activities. These peptides have shown no effects on the growth of oak mushrooms. When the peptide toxins were applied to the green mold, Trichoderma harzianum H1, they inhibited the growth of green molds. Among the 20 strains of peptide-forming P. tolaasii, strong, moderate, and weak antifungal activities were measured from 8, 5, and 7 strains, respectively. During oak mushroom cultivation, bacterial culture supernatants containing the peptide toxins were sprayed on the aerial mycelia of green molds grown on the surface of sawdust media. The culture supernatants were able to suppress the fungal growth of green molds while no effect was observed on the mushroom growth and production. They changed the color of molds from white aerial mycelium into yellowish dried scab, representing the powerful anti-fungal and sterilization activities of peptide toxins.

• Research in Plant Disease
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• v.22 no.2
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• pp.111-115
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• 2016

Wilt disease appeared the first in greenhouse-grown safflower (Carthamus tinctorius) in Jeonju, Korea. With the advancement of the disease, the infected plants were withered and died. In order to investigate the causal organism of this symptom disease, fungus was isolated from the infected plants and cultured on potato dextrose agar medium. The fungus showed the white or orange colony color with aerial mycelium. Macroconidia were from falcate to straight, usually 3-5 septate with $38.0-66.7{\times}2.9-4.4{\mu}m$. The fungus was inoculated to a new safflower plant and caused the same wilt. With morphological characters and pathogenicity results, sequence analyses (internal transcribed spacer ribosomal DNA and translation elongation factor $1{\alpha}$) suggested that, the isolated fungus is Fusarium proliferatum. This is the first report of Fusarium wilt disease caused by F. proliferatum on safflower in Korea.

• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.325-332
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• 1998

In vitro phosphorylation experiments with a cell extract of Streptomyces coelicolor A3(2) M130 in the presence of ${\gamma}-[^32P]$]ATP revealed the presence of multiple phosphorylated proteins, including the AfsR/AfsK kinases which control the biosynthesis of A-factor, actinorhodin, and undecylprodigiosin. Phosphorylation of AfsR by a cell extract as an AfsK source was significantly inhibited by Ser/Thr protein kinase inhibitors, staurosporine and K-252a, at concentrations giving 50% inhibition ($IC_50$) of $1{\mu}M\;and\;0.1{\mu}M$, respectively. Further in vitro experiments with the cell extracts showed that phosphorylation of multiple proteins was inhibited by various protein kinase inhibitors with different inhibitory profiles. Manganese and calcium ions in the reaction mixture also modulate phosphorylation of multiple proteins. Manganese at 10 mM greatly enhanced the phosphorylation and partially circumvented the inhibition caused by staurosporine and K-252a. A calcium-activated protein kinase(s) was little affected by these inhibitors. Herbimycin and radicicol, which are known as tyrosine kinase inhibitors, did not show any significant inhibition of AfsR phosphorylation. Consistent with the in vitro effect of the kinase inhibitors, they inhibited aerial mycelium formation and pigmented antibiotic production on solid media. On the contrary, when assayed in liquid culture, the amount of actinorhodin produced was increased by staurosporine and K-252a and greatly decreased by manganese. All of these data clearly show that the genus Streptomyces possesses several protein kinases of eukaryotic types which are involved in the regulatory network for morphogenesis and secondary metabolism.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.71-76
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• 2002

Soil samples were screened for actinomycete strains capable of producing phospholipase D, and a strain, Streptomyces sp. YU100, showing a high transphosphatidylation activity was isolated. This strain secreted phospholipase D in a culture broth after 12 h of cultivation, and its productivity continued to increase for 36 h of fermentation. In addition, its transphosphatidylation rate of phosphatidylcholine to phosphatidylserine was almost $68\%$ within 1 h. The morphological and chemotaxonomical characteristics showed that this strain could be classified as a number of the Streptomycetaceae family, particularly due to the spiral form of its spore chain consisting of 60-70 smooth spores $(0.75{\times}1.0{\mu}m$) on an aerial mycelium, FA-2c type of fatty acid profile in the cell wall, and LL-DAP component in the cell wall peptidoglycan. A phylogenetic analysis of the 16S rDNA provided a clue that the strain YU100 was actually a member of the genus Streptomyces, because the determined sequence exhibited a higher homology with Streptomyes sp. ASB27, S. peucetius JCM9920, and S. griseus ATCC10137. A dendrogram based on the 16S rDNA sequences also showed a phylogenetic relationship between the strain YU100 and these strains. However, the strain YU100 has not yet been assigned to a particular species, because of absence of any other classified species with a high matching score.