• Journal of Microbiology and Biotechnology
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• v.24 no.9
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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.

• Natural Product Sciences
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• v.21 no.4
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• pp.261-267
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• 2015

Compared to their terrestrial and marine counterparts, little is known about the capacity of freshwater-derived actinomycete bacteria to produce novel secondary metabolites. In the current study, we highlight the disparities that exist between cultivation-independent and -dependent analyses of actinomycete communities from four locations in Lake Michigan sediment. Furthermore, through phylogenetic analysis of strains isolated from these locations, we identified a Streptomyces sp., strain B025, as being distinct from other Streptomyces spp. isolated from sediment. Upon fermentation this strain produced a rare class of eight-membered lactone secondary metabolites, which have been for their antitumor properties. We used spectroscopic and chemical derivitization techniques to characterize octalactin B (1) in addition to its corresponding novel, unnatural degradation product (2).

• Korean Journal Plant Pathology
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• v.14 no.3
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• pp.191-202
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• 1998

About 300 actinomycetes were isolated from two forest and one sea-shore soil and tested for inhibitory effects on mycelial growth of six plant pathogenic fungi Magnaporthe grisea, Alternaria mali, Colletotrichum gloeosporioides, Phytophthora capsici, Fusarium oxysporum f. sp. cucumerinum, and Rhizoctonia solani. Among 300 actinomycetes tested, only 16 actinomycetes showed the antifungal activity against the test fungi. Isolate NH 50 was selected for production and purification of antifungal antibiotic substances. Actinomycete isolate NH 50 displayed the broad antifungal spectra against 11 plant pathogenic fungi. To identify actinomycete isolate NH 50, cultural characteristics on various agar media, diaminopimelic acid type, and morphological characteristics by scanning electron microscopy were examined. As a result, actinomycete isolate NH 50 was classified as a rare actinomycete that had LL-DAP type and did not produce spores. After incubation of isolate NH 50 in yeast extract-malt extract-dextrose broth, antifungal compound NH-B1 that inhibited mycelial growth of some plant pathogenic fungi was purified from the methanol eluates of XAD-16 resins by a series of purification procedures, i.e., silica gel flash chromatography, C18 flash chromatography, Sephadex LH-20 column chromatography, silica gel medium pressure liquid chromatography (MPLC), C18 MPLC, and high pressure liquid chromatography (HPLC). UV spectrum and 1HNMR spectrum of antifungal compound NH-B1 dissolved in methanol were examined. The antibiotic NH-B1 showed the major peaks at 230 and 271.2nm. Based on the data of 1H-NMR spectrum, NH-B1 was confirmed to be an extremely complex polymer of sugars called polysaccharides. The antibiotic NH-B1 showed strong antifungal activity against Alternaria solani and Cercospora kikuchi, but weak activity against M. grisea.

• Journal of Microbiology
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• v.39 no.1
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• pp.17-23
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• 2001

Various pretreatment procedures and selective media were applied to assess the optimal conditions for the isolation of rare actinomycetes from soil. Pretreatment of wet-heating for 15 min at 70$^{\circ}C$ and phenol treatment of soil suspension were the most effective methods for the isolation of these microorganisms. Hair hydrolysate vitamin agar (HHVA) was the most suitable medium for the recovery of rare actinomycetes. Thirty-five rare actinomycete strains were chosen using selective isolation approaches, then morphological and chemical properties of the isolates were determined. The isolates belonged to one of the following genus, Micromonospora, Microbispora, Actinoplanes and Streptosporangium.

• Microbiology and Biotechnology Letters
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• v.24 no.5
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• pp.534-539
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• 1996

Total 276 soil actinomycete strains were isolated from 46 soil samples collected at domestic natural caves; the Kosu, Chundong, and Nodong caves at Chungbook province, the Kossi cave at Kangwon province, the Sungruye cave at Kyungbook province, the Hyupjae, Ssangyong, and Manjang caves at Cheju province. All of these isolates were identified to the genus level based on morphological and physiological characteristics. As the result, 52.5% of those isolates were Streptomyces, 16.3% were Micromonospora, 22.8% were Nocardioform group, 1.1% were Actinomadura, 0.3% were Nocardiopsis, 0.3% were Streptosporangium, 0.3% were Nocardioides, 1.4% were Kineosporia, 4.7% were the others. Streptomycete strains were the most abundant, but were relatively less comparing to general distribution pattern. Nocardioform and Micromonospora strains were quite abundant, and other rare actinomycete groups were somewhat abundant comparing to general distribution pattern previously reported. Especially Nocardioform strains were highly abundant at almost of the natural caves.

• Microbiology and Biotechnology Letters
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• v.28 no.3
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• pp.129-133
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• 2000

Different actinomycete strains were isolated from natural lime caves of Ondal Chemongok Hwanseon and Yongyeon which are located at Kangwon or chungcheongbook province in Korea and were identified to the genus level. Soil sam-ples were collected at 6 sites inside and 2 sites outside of each natural lime cave, As the result the strains belonging to genus Streptomyces and rare actinomycetes were isolated at the average of 2.1 and 3.4 strains per g soil on inside cave whereas which were isolated at the 6.0 and 1.8 strains per g soil on outside cave. How-ever the generic distribution of Streptomyces and rare actinomycetes isolated from outside cave was quite dif-ferent from that of inside cave. It was shown that rare actinomycetes at natural lime caves is generally highly abundant than Streptomyces.

• Korean Journal of Microbiology
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• v.34 no.3
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• pp.149-153
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• 1998

From soils seasonally collected at two depths (0~2 cm, $50{\pm}1cm$) of forest, field, grass land, or paddy field, distinct strains of actinomycetes were isolated and identified to the genus level. The genus-diversity of soil actinomycetes was revealed to be considerably different by seasonal change. It was also affected by soil depths, soil types, or actinomycete groups. At the soil depth of 0~2 cm, the seasonal distribution fluctuation (%) of streptomycete strains was higher in grass land (41%), field (39%) soil than paddy field (18%), or forest (18%), whereas that of streptomycete strains at the soil depth of $50{\pm}1cm$ was high in order of paddy field (36%), field (28%), grass land (26%), and forest (16%). On the other hand, the seasonal distribution fluctuation ratio of rare actinomycete strains at the soil depth of 0~2 cm was above 45% except for paddy field (26%). At the soil depth of $50{\pm}1cm$, the seasonal distribution of rare actinomycete strains exhibited high fluctuation (%) in order of forest (79%), paddy field (36%), field (24%), and grass land (10%).

• Journal of Microbiology and Biotechnology
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• v.15 no.5
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• pp.1140-1145
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• 2005

MJM383, a rare actinomycete sp. strain originated from Chinese soils, was isolated through an antimicrobial screening system. The analysis of 16S rDNA sequences and biochemical characterization determined the strain to belong to genus Kitasatospora. Both NMR and ESI mass data of its purified bioactive compounds revealed Kitasatospora sp. MJM383 to produce two antitumor agents, streptonigrin and oxopropaline G, which have been known to be produced from Streptomyces species. This is the first report to demonstrate the presence of antitumor agents produced by genus Kitasatospora.

• Mycobiology
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• v.39 no.3
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• pp.174-181
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• 2011

The purpose of the present study was to investigate the influence of cultural and environmental parameters affecting the growth and bioactive metabolite production of the rare strain VUK-10 of actinomycete Pseudonocardia, which exhibits a broad spectrum of in vitro antimicrobial activity against bacteria and fungi. Production of bioactive metabolites by the strain was high the in modified yeast extract-malt extract-dextrose (ISP-2) broth, as compared to other tested media. Glucose (1%) and tryptone (0.25%) were found to be the most suitable carbon and nitrogen sources, respectively, for optimum production of growth and bioactive metabolites. Maximum production of bioactive metabolites was found in the culture medium with initial pH 7 incubated with the strain for four days at $30^{\circ}C$, under shaking conditions. This is the first report on the optimization of bioactive metabolites by Pseudonocardia sp. VUK-10.