• Korean Journal of Environmental Agriculture
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• v.40 no.1
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• pp.20-32
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• 2021

BACKGROUND: Bacterial shot hole of stone fruits is a seriuos plant disease caused by Xanthomonas arboricola pv. pruni (Xap). Techniques to control the disease are required. In this study, microorganisms with antibacterial activity were isolated to develop as a microbial agent against the bacterial shot hole. METHODS AND RESULTS: An isolate with the strongest activity among the isolates was identified as Streptomyces avidinii based on 16S rRNA gene sequence analysis and designated Streptomyces sp. J46. J46 showed suppression of bacterial leaf spot with a control value of 90% at 10 times-diluted cell free supernatant. To investigate antibacterial metabolites produced by J46, the supernatant of J46 was extracted with organic solvents, and the extracts were subjected to chromatography works. Antibacterial metabolites were not extractable with organic solvents. Both reverse and normal phase techniques were not successful because the metabolites were extremely water soluble. The antibacterial metabolites were not volatiles but protein compounds based on hydrolysis enzyme treatment. CONCLUSION: Our study suggests that Streptomyces sp. J46 may be a potential as an microbial agent against bacterial shot hole. Further study to identify the metabolites is required in more detail.

• IMMUNE NETWORK
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• v.23 no.1
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• pp.7.1-7.27
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• 2023

The mammalian intestines harbor trillions of commensal microorganisms composed of thousands of species that are collectively called gut microbiota. Among the microbiota, bacteria are the predominant microorganism, with viruses, protozoa, and fungi (mycobiota) making up a relatively smaller population. The microbial communities play fundamental roles in the maturation and orchestration of the immune landscape in health and disease. Primarily, the gut microbiota modulates the immune system to maintain homeostasis and plays a crucial role in regulating the pathogenesis and pathophysiology of inflammatory, neuronal, and metabolic disorders. The microbiota modulates the host immune system through direct interactions with immune cells or indirect mechanisms such as producing short-chain acids and diverse metabolites. Numerous researchers have put extensive efforts into investigating the role of microbes in immune regulation, discovering novel immunomodulatory microbial species, identifying key effector molecules, and demonstrating how microbes and their key effector molecules mechanistically impact the host immune system. Consequently, recent studies suggest that several microbial species and their immunomodulatory molecules have therapeutic applicability in preclinical settings of multiple disorders. Nonetheless, it is still unclear why and how a handful of microorganisms and their key molecules affect the host immunity in diverse diseases. This review mainly discusses the role of microbes and their metabolites in T helper cell differentiation, immunomodulatory function, and their modes of action.

• Journal of Microbiology and Biotechnology
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• v.16 no.6
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• pp.870-879
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• 2006

The present study describes the formation of succinic acid by a nonvirulent, highly osmotolerant Klebsiella pneumoniae strain SAP (succinic acid producer), its profile of metabolites, and enzymes of the succinate production pathway. The strain produced succinate along with other metabolites such as lactate, acetate, and ethanol under aerobic as well as anaerobic growth conditions. The yield of succinate was higher in the presence of $MgCO_3$ under $N_2$ atmosphere as compared with that under $CO_2$ atmosphere. Analysis of intracellular metabolites showed the presence of a smaller PEP pool than that of pyruvate. Oxaloacetate, citrate, and $\alpha$-ketoglutarate pools were considerably larger than those of isocitrate and fumarate. In order to understand the synthesis of succinate, the enzymes involved in end-product formation were studied. Levels of phosphoenolpyruvate carboxykinase, fumarate reductase, pyruvate kinase, and acetate kinase were higher under anaerobic growth conditions. Based on the profiles of the metabolites and enzymes, it was concluded that the synthesis of succinate took place via oxaloacetate, malate, and fumarate in the strain under anaerobic growth conditions. The strain SAP showed potential for the bioconversion of fumarate to succinate under $N_2$ atmosphere in the presence of $MgCO_3$. At an initial fumarate concentration of 10 g/l, 7.1 g/l fumarate was converted to 7 g/l succinate with a molar conversion efficiency of 97.3%. The conversion efficiency and succinate yield were increased in the presence of glucose. Cells grown on fumarate contained an 18-fold higher fumarate reductase activity as compared with the activity obtained when grown on glucose.

• Journal of Microbiology and Biotechnology
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• v.25 no.5
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• pp.672-680
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• 2015

As a global regulatory gene in Streptomyces, afsR can activate the biosynthesis of many secondary metabolites. The effect of afsR on the biosynthesis of a phenazine metabolite, lomofungin, was studied in Streptomyces lomondensis S015. There was a 2.5-fold increase of lomofungin production in the afsR-overexpressing strain of S. lomondensis S015 N1 compared with the wild-type strain. Meanwhile, the transcription levels of afsR and two important genes involved in the biosynthesis of lomofungin (i.e., phzC and phzE) were significantly upregulated in S. lomondensis S015 N1. The optimization of metal chlorides was investigated to further increase the production of lomofungin in the afsR-overexpressing strain. The addition of different metal chlorides to S. lomondensis S015 N1 cultivations showed that CaCl₂, FeCl₂, and MnCl₂ led to an increase in lomofungin biosynthesis. The optimum concentrations of these metal chlorides were obtained using response surface methodology. CaCl₂ (0.04 mM), FeCl₂ (0.33 mM), and MnCl₂ (0.38 mM) gave a maximum lomofungin production titer of 318.0 ± 10.7 mg/l, which was a 4.1-fold increase compared with that of S. lomondensis S015 N1 without the addition of a metal chloride. This work demonstrates that the biosynthesis of phenazine metabolites can be induced by afsR. The results also indicate that metal chlorides addition might be a simple and useful strategy for improving the production of other phenazine metabolites in Streptomyces.

• Proceedings of the Korea Environmental Mutagen Society Conference
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• 2002.11a
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• pp.90-90
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• 2002

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2002.10a
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• pp.7-7
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.5-5
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• 1999

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.397-397
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• 2005

• Microbiology and Biotechnology Letters
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• v.36 no.4
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• pp.336-342
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• 2008

The effect of methyl tert-butyl ether (MTBE) and its metabolites like tert-butyl alcohol (TBA), and formaldehyde (FA) on microbial activity and diversity in tidal mud flat was studied. MTBE, TBA, and FA with different concentrations were added into microcosms containing tidal mud samples, and placed at room temperature for 30 days. Then the physico-chemical properties such as pH, moisture contents and organic matter contents in the microcosms were measured. In addition, the total viable cell number and dehydrogenase activity were measured. Bacterial communities in the microcosms were monitored using a 16S rRNA-PCR-DGGE (Denaturing gradient gel electrophoresis) fingerprinting method. As a result, the exposure concentrations of MTBE and its metabolites showed no correlation with the physico-chemical factors (P>0.05). Dehydrogenase activity and total viable cell number were decreased with increasing MTBE, TBA and FA concentrations (P<0.05). The toxic effect was higher the following order: FA > MTBE > TBA. Dominant species in the microcosms contaminated with MTBE and its metabolites were Sphingobacteria, Flavobacteria, delta-proteobacteria, gamma-proteobacteria. The diversity of bacterial community was not significantly influenced by MTBE and its metabolites.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.922-931
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• 2009

Screening-scale studies were performed with 26 fungal cultures for their ability to transform the anti-inflammatory drug meloxicam. Among the different fungi screened, a filamentous fungus, Cunninghamella blakesleeana NCIM 687, transformed meloxicam to three metabolites in significant quantities. The transformation of meloxicam was confirmed by high-performance liquid chromatography (HPLC). Based on the liquid chromatography-tandem mass spectrometry (LC-MS/MS) data, two metabolites were predicted to be 5-hydroxymethyl meloxicam and 5-carboxy meloxicam, the major mammalian metabolites reported previously. A new metabolite was produced, which is not detected in mammalian systems. Glucose medium, pH of 6.0, temperature of $27^{\circ}C$, 5-day incubation period, dimethylformamide as solvent, and glucose concentration of 2.0% were found to be suitable for maximum transformation of meloxicam when studied separately. It is concluded that C. blakesleeana can be employed for biotransformation of drugs for production of novel metabolites.