• 한국미생물·생명공학회지
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• 제28권3호
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• pp.161-166
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• 2000

Monilinia fructicola에 의해 감염되어 미이라화된 복숭아 열매로부터 Monilinia fructicola에 강한 항진균성 물질 chitinase 및 urease을 분비하는 방선균을 분리하였다 선발된 TH-04 균주는 배양적 .형태적 특성 세포벽 성분 및 세포내 당 성분을 분석한 결과 전형적인 Streptomyces속에 속하는 방선균으로 동정되었다. TH-04 균주는 Monilinia fructicola Colletotrichum gloeosporioides Magnaporthe grisea Rhizoctonia solani, Phytophthora capsici, Alternaria kikuchi-ana, Fusarium solani 및 Fusarium oxysporum 등 8종의 식물병원균에 대하여 항진균 활성을 나타냈다. 항생물질 생산을 위한 배양조건은 온도 $20^{\circ}C$, pH 7 및 배양기간 7일로 확인되었다.

• Journal of Microbiology and Biotechnology
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• 제7권6호
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• pp.397-401
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• 1997

The present research program was conducted to characterize a strain of actinomycetes producing an anti methicillin-resistant Staphylococcus aureus (MRSA) antibiotic. Soil samples were collected from various sites in Korea and a number of actinomycetes were isolated from the soil samples by applying selective agar for actinomycetes. Among over 400 isolates, a strain (AMLK-135) producing anti-MRSA antibiotic against S. aureus TK 784 was selected. According to the morphological and physiological characteristics, the strain AMLK-135 was confirmed to belong to the genus Streptomyces. From the results of species identification with the TAXON program, the strain AMLK-135 was shown to belong to major cluster 5 (Streptomyces exfoliatus), but it had a low simple matching coefficient ($S_{SM}$ SM/) value to member organisms of major cluster 5. Percentage ($\%$) of strain further away of the strain AMLK-135 was low (1.9400) and it was placed further away than the outer-most members in major cluster 5. Therefore, the strain AMLK-135 was identified as a new species of the genus Streptomyces.

• Journal of Microbiology and Biotechnology
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• 제24권9호
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• pp.1226-1231
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• 2014

The rare actinomycete Pseudonocardia autotrophica was previously shown to produce a solubility-improved toxicity-reduced novel polyene compound named $\underline{N}ystatin$-like $\underline{P}seudonocardia$ $\underline{P}olyene$ (NPP). The low productivity of NPP in P. autotrophica implies that its biosynthetic pathway is tightly regulated. In this study, $wblA_{pau}$ was isolated and identified as a novel negative regulatory gene for NPP production in P. autotrophica, which showed approximately 49% amino acid identity with a global antibiotic down-regulatory gene, wblA, identified from various Streptomycetes species. Although no significant difference in NPP production was observed between P. autotrophica harboring empty vector and the S. coelicolor wblA under its native promoter, approximately 12% less NPP was produced in P. autotrophica expressing the wblA gene under the strong constitutive $ermE^*$ promoter. Furthermore, disruption of the $wblA_{pau}$ gene from P. autotrophica resulted in an approximately 80% increase in NPP productivity. These results strongly suggest that identification and inactivation of the global antibiotic down-regulatory gene wblA ortholog are a critical strategy for improving secondary metabolite overproduction in not only Streptomyces but also non-Streptomyces rare actinomycete species.

• Journal of Microbiology and Biotechnology
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• 제18권11호
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• pp.1741-1746
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• 2008

This study was conducted to select endophytic actinomycetes as biocontrol agents against Chinese cabbage clubroot caused by Plasmodiophora brassicae. A total of 81 endophytic actinomycetes were isolated from surface-sterilized roots of Chinese cabbage that was grown on paddy field and upland soils collected from various locations in Korea. By using 16S ribosomal DNA (rDNA) gene sequencing, they were classified to 8 actinobacterial genera. The genus Microbispora (67%) was most frequently isolated, followed by Streptomyces (12%) and Micromonospora (11%). Three of the 81 isolates, when inoculated in germinated Chinese cabbage seeds and then transplanted to pots, effectively suppressed the occurrence of a post-inoculated strain of P. brassicae in the pots. They showed control values of 58% for strain A004, 33% for strain A011, and 42% for strain A018. Based on cell wall components, morphological characteristics, and phylogenetic analyses, the three antagonistic isolates were identified as Microbispora rosea subsp. rosea (A004 and A011) and Streptomyces olivochromogenes (A018). Further researches on the field efficacy and action modes of the three actinomycetes are in progress.

• 한국미생물·생명공학회지
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• 제38권4호
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• pp.475-480
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• 2010

Actinomycetes are Gram-positive soil bacteria and one of the most important industrial microorganisms due to superior biosynthetic capabilities of many valuable secondary metabolites as well as production of various valuable bioconversion enzymes. Among them are cytochrome P450 hydroxylase (CYP), which are hemoproteins encoded by a super family of genes, are universally distributed in most of the organisms from all biological kingdoms. Actinomycetes are a rich source of soluble CYP enzymes, which play critical roles in the bioactivation and detoxification of a wide variety of metabolite biosynthesis and xenobiotic transformation. Cyclosporin A (CyA), one of the most commonly-prescribed immunosuppressive drugs, was previously reported to be hydroxylated at the position of 4th N-methyl leucine by a rare actinomycetes called Sebekia benihana, leading to display different biological activity spectrum such as loss of immunosuppressive activities yet retaining hair growth-stimulating side effect. In order to improve this regio-selective CyA hydroxylation in S. benihana, previously-identified several secondary metabolite up-regulatory genes from Streptomyces coelicolor and S. avermitilis were heterologously overexpressed in S. benihana using an $ermE^*$ promoter-containing Streptomyces integrative expression vector. Among tested, SCO4967 encoding a conserved hypothetical protein significantly stimulated region-specific CyA hydroxylation in S. benihana, implying that some common regulatory systems functioning in both biosynthesis and bioconversion of secondary metabolite might be present in different actinomycetes species.

• 한국미생물·생명공학회지
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• 제50권2호
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• pp.255-269
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• 2022

Actinomycetes isolated from marine habitats represent a promising source of bioactive substances. Here, we report on the isolation, identification, productivity enhancement and application of the bioactive compounds of Streptomyces qinglanensis H4. Eighteen marine actinomycetes were isolated and tested for resistance to seven bacterial diseases. Using 16S rRNA sequencing analysis (GenBank accession number MW563772), the most powerful isolate was identified as S. qinglanensis. Although the strain produced active compound(s) against a number of Gram-negative and Gram-positive bacteria, it failed to inhibit pathogenic fungi. The obtained inhibition zones were 22.0 ± 1.5, 20.0 ± 1, 16.0 ± 1, 12.0 ± 1, 22.0 ± 1 and 24.0 ± 1 mm against Bacillus subtilis ATCC 6633, Escherichia coli ATCC 19404, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 10231 and Staphylococcus aureus ATCC6538, respectively. To maximize bioactive compound synthesis, the Plackett-Burman design was used. The productivity increased up to 0.93-fold, when S. qinglanensis was grown in optimized medium composed of: (g/l) starch 30; KNO₃ 0.5; K₂HPO₄ 0.25; MgSO₄ 0.25; FeSO₄·7H₂O, 0.01; sea water concentration (%) 100; pH 8.0, and an incubation period of 9 days. Moreover, the anticancer activity of S. qinglanensis was tested against two different cell lines: HepG2 and CACO. The inhibition activities were 42.96 and 57.14%, respectively. Our findings suggest that the marine S. qinglanensis strain, which grows well on tailored medium, might be a source of bioactive substances for healthcare companies.

• Journal of Microbiology and Biotechnology
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• 제17권12호
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• pp.1909-1921
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• 2007

Significant progress has recently been made concerning the engineering of deoxysugar biosynthesis. The biosynthetic gene clusters of several deoxysugars from various polyketides and aminoglycosides-producing microorganisms have been cloned and studied. This review introduces the biosynthetic pathways of several deoxysugars and the generation of novel hybrid macrolide antibiotics via the coexpression of deoxysugar biosynthetic gene cassettes and the substrate-flexible glycosyltransferases in a host organism as well as the production of TDP-deoxysugar derivatives via one-pot enzymatic reactions with the identified enzymes. These recent developments in the engineering of deoxysugars biosynthesis may pave the way to create novel secondary metabolites with potential biological activities.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.677-684
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• 2001

To isolate mutanse-producing bacteria, soil samples were collected from several areas in chonnam Province, South Korea. A total of 70 strains of actinomycetes were isolated from the soil samples. All isolated actinomycetes were inoculated on mutanase screening media to identify new bacterial strains producing mutanase activity. One strain in particular exhibited a strong mutanase-producing activity, and was identified as Microbispora rosea based on its morphological, cultural, and physiological characteristics, and also by 16S rDNA sequences.

• 한국미생물·생명공학회지
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• 제27권3호
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• pp.215-222
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• 1999

Methylotrophic actinomycetes No. 155 produced an aminoglycoside antibiotics(AG)-resistant inhibitor. We have previously reported that the inhibitor shows strong inhibition to sisomicin-resistant strain. In order to understand the functions of inhibitor and sisomicin-resistance, characterizations and purification of inhibitor were investigated. Strain No. 155 was tentatively identified as Nocardiopsis sp. based on morphological and some physiological characteristics. In the antimicrobial activity test, the addition of inhibitor to sisomicin showed a reduction effect of MIC on the test strains such as Gram(+), Gram(-) bacteria and yeasts. The combination of the inhibitor and various antibiotics revealed synergistic against E. coli K-12 and B. subtilis PCI 219. The induced intracellular proteins from sisomicin-resistant strain exhibited the sisomicin inactivation by invitro test. And the induced intracellular proteins were inactivated by addition of the inhibitor. The inhibitor compound was purified by anion exchange chromatography(Dowex-1) and HPLC using Asahipak ES-502C column. The purified inhibitor compound was detected in a single peak(above 98.5% purity) through the HPLC analysis.

• 한국미생물·생명공학회지
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• 제14권5호
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• pp.377-383
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• 1986

토양으로부터 carboxymethyl cellulase 및 intra-cellular $\beta$-glucosidase생산능력이 높은 방선균 No. 109균주를 분리하고 이 균주의 배양상 내지는 형태적 특성, 생리적 특성 그리고 세포벽 구성성분 등을 조사, 균동정을 행한 결과 No. 109 분리균은 Streptomyces tanashiensis 또는 그 유연균으로 동정되었다.