• Microbiology and Biotechnology Letters
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• v.5 no.1
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• pp.36-45
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• 1977

A piscicidal substance was isolated from the culture medium of Streptomyces umbrosus by avicel column chromatography and avicel thin layer chromatography after extration with chroloform. Bluegreen fluorescence was emitted under UV irradiation. Factors which govern toxin production and nutrition requirement for high toxin titres were observed. Nutritional uptake for toxin production was not curresponded with that for cell growth. Alanine, valine, serine asparagine, arginine, histidine, urea and sodium nitrate as a carbon source and glucose, mannose, rhamnose, xylose, arabitol and starch as a carbon source were recognized as a favorable nutrient for high toxin production. Magnesium was essential factor whereas vitamins were not of effective. Most of toxin was formed simultaneously with cell growth in esponential phase. Maximal production was observed for six day culture at 3$0^{\circ}C$. Tissues of gill, kidney and pnacreas in Cyprinus carpio were denatured extreamly after treating with the substance. Atrophied nucleous, indented membrane and degradated cytoplasm with necrotic affectness were noted on each tissue. The chemical formula of the substance was designated as $C_{38}$ $H_{66}$ $NO_4$.

• Journal of Microbiology and Biotechnology
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• v.26 no.6
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• pp.1103-1108
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• 2016

Yam anthracnose caused by Colletotrichum gloeosporioides (C.g) is the most devastating disease of yam (Dioscorea sp.). In the present study, we evaluated the culture filtrate extract (CFE) of azalomycin-producing Streptomyces malaysiensis strain MJM1968 for the control of yam anthracnose. MJM1968 showed strong antagonistic activity against C.g in vitro. Furthermore, the MJM1968 CFE was tested for inhibition of spore germination in C.g, where it completely inhibited spore germination at a concentration of 50 μg/ml. To assess the in planta efficacy of the CFE and spores of MJM1968 against C.g, a detached leaf bioassay was conducted, which showed both the treatments suppressed anthracnose development on detached yam leaves. Furthermore, a greenhouse study was conducted to evaluate the CFE from MJM1968 as a fungicide for the control of yam anthracnose. The CFE non-treated plants showed a disease severity of >92% after 90 days of artificial inoculation with C.g, whereas the disease severity of CFE-treated and benomyl-treated yam plants was reduced to 26% and 15%, respectively, after 90 days. Analysis of the yam tubers from the CFE-treated and non-treated groups showed that tubers from the CFE-treated plants were larger than that of non-treated plants, which produced abnormal smaller tubers typical of anthracnose. This study demonstrated the utility of the CFE from S. malaysiensis strain MJM1968 as a biofungicide for the control of yam anthracnose.

• Microbiology and Biotechnology Letters
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• v.3 no.2
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• pp.63-68
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• 1975

A biological active substance was isolated from the cultured medium of Streptomyces sp. and its biochemical characteristics were investigated. Isolation process of the substance was as follows; the pH of filterate of the cultured medium was adjusted to 3.0 with N-hydrochloric acid and saturated with sodium chloride, then chloroform was added to this filterate in one fifth portions and stirred vigorously. After extracting the active substance with chloroform in 3 stages, the chloroform layer combined and evaporatea after dehydrating with sodium sulfate. The substance was found to be to be toxic to various fresh water fishes; the lethal dose for an average size Pseudorasbora parva T. et. S. was 50ug per ml. In the acidic condition, the toxicity of the substance remained fora long time, while in the alkaline state, the toxicity was decreased very fast. This substance was found to be stable to organic solvents, but labile to heat treatment. The maximal revival time of Pseudorasbora parva T. et. S. was about 20 minutes in 25 ug/ml of the substance solution.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.108-122
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• 2023

Fusarium oxysporum f. sp. lycopersici (Fol) and Fusarium oxysporum f. sp. cubense (Foc), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the Streptomyces-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of Fol and Foc. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in Fol inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in Foc inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.

• 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.

• Journal of Microbiology and Biotechnology
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• v.30 no.7
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• pp.1082-1091
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• 2020

Microbial transglutaminases (MTGs) are widely used in the food industry. In this study, the MTG gene of Streptomyces sp. TYQ1024 was cloned and expressed in a food-grade bacterial strain, Bacillus subtilis SCK6. Extracellular activity of the MTG after codon and signal peptide (SP Ync M) optimization was 20 times that of the pre-optimized enzyme. After purification, the molecular weight of the MTG was 38 kDa and the specific activity was 63.75 U/mg. The optimal temperature and pH for the recombinant MTG activity were 50℃ and 8.0, respectively. MTG activity increased 1.42-fold in the presence of β-ME and 1.6-fold in the presence of DTT. Moreover, 18% sodium chloride still resulted in 83% enzyme activity, which showed good salt tolerance. Cross-linking gelatin with the MTG increased the strength of gelatin 1.67 times and increased the thermal denaturation temperature from 61.8 to 75.8℃. The MTG also significantly increased the strength and thermal stability of gelatin. These characteristics demonstrated the huge commercial potential of MTG, such as for applications in salted protein foods.

• Asian Journal of Turfgrass Science
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• v.26 no.1
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• pp.8-16
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• 2012

The objective of this study was to identify bacterial antagonists of R. solani AG2-2 (IV) on zoysiagrass and to evaluate their antifungal activity in vitro and in vivo to select an antagonistic isolate. Antagonistic isolates that inhibit large patch disease caused by R. solani AG2-2 (IV) in zoysiagrass were selected from several soils, and their antagonistic activities were investigated in vitro and in vivo. Of 216 bacterial isolates, 67 inhibited several plant pathogenic fungi. The isolates that inhibited stem-segment colonization by R. solani AG2-2 (IV) in zoysiagrass were tested in a growth chamber. Eleven isolates were active as plant growth promoting isolates. Among them, five plant growth promoting isolates and their concentration dependent efficiency on zoysiagrass following inoculation with R. solani AG2-2 (IV) was evaluated. Isolate H33 was one of the potential antagonistic isolates, and it was further tested against various plant pathogens. H33 not only suppressed the disease caused by R. solani AG2-2 (IV) on zoysiagrass but also promoted leaf weight and leaf height of zoysiagrass under growth chamber and greenhouse conditions. The H33 isolate, which belongs to Streptomyces arenae, was identified through physiological, biochemical, and 16S rDNA studies. Further studies will investigate the cultural characterization of S. arenae H33 and isolation and identification of antifungal substance produced by S. arenae H33.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1077-1084
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• 2009

A genomic library was constructed to clone a xylanase gene (Mxyn10) from Demequina sp. JK4 isolated from a deep sea. Mxyn10 encoded a 471 residue protein with a calculated molecular mass of 49 kDa. This protein showed the highest sequence identity (70%) with the xylanase from Streptomyces lividans. Mxyn10 contains a catalytic domain that belongs to the glycoside hydrolase family 10 (GH10) and a carbohydrate-binding module (CBM) belonging to family 2. The optimum pH and temperature for enzymatic activity were pH 5.5 and $55^{\circ}C$, respectively. Mxyn10 exhibited good pH stability, remaining stable after treatment with buffers ranging from pH 3.5 to 10.0. The protein was not significantly affected by a variety of chemical reagents, including some compounds that usually inhibit the activity of other related enzymes. In addition, Mxyn10 showed activity on cellulose. These properties mark Mxyn10 as a potential enzyme for industrial application and saccharification processes essential for bioethanol production.

• Journal of Microbiology and Biotechnology
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• v.33 no.7
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• pp.949-954
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• 2023

Type III polyketide synthase (PKS) found in bacteria is known as 1,3,6,8-tetrahydroxynaphthalene synthase (THNS). Microbial type III PKSs synthesize various compounds that possess crucial biological functions and significant pharmaceutical activities. Based on our sequence analysis, we have identified a putative type III polyketide synthase from Nocardia sp. CS682 was named as ThnA. The role of ThnA, in Nocardia sp. CS682 during the biosynthesis of 1,3,6,8 tetrahydroxynaphthalene(THN), which is the key intermediate of 1-(α-L-(2-O-methyl)-6-deoxymannopyranosyloxy)-3,6,8-trimethoxynaphthalene (IBR-3) was characterized. ThnA utilized five molecules of malonyl-CoA as a starter substrate to generate the polyketide 1,3,6,8-tetrahydroxynaphthalene, which could spontaneously be oxidized to the red flaviolin compound 2,5,7-trihydroxy-1,4-naphthoquinone. The amino acid sequence alignment of ThnA revealed similarities with a previously identified type III PKS and identified Cys¹³⁸, Phe¹⁸⁸, His²⁷⁰, and Asn³⁰³ as four highly conserved active site amino acid residues, as found in other known polyketide synthases. In this study, we report the heterologous expression of the type III polyketide synthase thnA in S. lividans TK24 and the identification of THN production in a mutant strain. We also compared the transcription level of thnA in S. lividans TK24 and S. lividans pIBR25-thnA and found that thnA was only transcribed in the mutant.

• Archives of Pharmacal Research
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• v.19 no.4
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• pp.261-263
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• 1996

SK-302B, an antibiotic purified from soil Streptomyces sp. 302, was structurally identified as echinomycin (C/sub 50/H/sub 66/N/sub 11/S/sub 2/). In the present experiment, the possibility of SK-302B as an anticolon cancer agent was investigated by using chemosensitivity system (MTT assay, clonogenic assay). Treatment of SK-302B on various colon cancer cell lines resulted in a significant cytotoxicity and tumor colony formation inhibition. These studies showed that SK-302B had a potent inhibition on colon cancer cells.