• Korean Journal of Organic Agriculture
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• v.9 no.4
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• pp.135-148
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• 2001

Antibiotics supplementation in animal feeds results in bacterial resistance to the antibiotics and residue of the antibiotics in animal products, which can cause serious problems in human health. Therefore, the finding of new substances replacing antibiotics are needed. New substances are egg york antibody, probiotics, organic acid, mannanoligosaccharide(MOS), fructooligosaccharide(FOS), and chitosan etc. Egg york antibody is antibody to obtain from egg york of the chicken injected the specific antigen. Probiotics can prevent the problems of residue of the antibiotics and resistance to the antibiotics. Organic acids ctrl preservation of colostrum inhibit the rottenness and increase the beneficial bacteria. MOS and FOS increase the beneficial bacteria, too. Chitosan is used the immune material to active the anti-bacteria.

• Journal of Microbiology and Biotechnology
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• v.4 no.4
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• pp.349-353
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• 1994

An isolate 90-GT-302, identified as Kitasatosporia kimorexae, was found to produce antibiotics that induce mycelial swelling in Magnaporthe grisea, and Fusarium solani. The strain produced at least 5 antibiotics. Among them, the main active compound designated as kimorexin A was isolated and its physico-chemical properties and biological activities were examined, and as a result was found to be of the thiopeptide antibiotic. A comparison between the properties of kimorexin A and those of the known thiopeptide antibiotics led us to conclude that kimorexin A was a new thiopeptide polythiazolyl antibiotic. Kimorexin A showed a narrow antimicrobial spectrum against very limited genus of phytopathogenic fungi. It prevented host plants from infections of Rhizoctonia solani and absolute parasitic fungi, such as Sphaerotheca fuliginea and Puccinia recondita, almost completely at the treatment concentration of approximately 20 ppm.

• Proceedings of the PSK Conference
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• 2000.04a
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• pp.191.3-192
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• 2000

• YAKHAK HOEJI
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• v.45 no.3
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• pp.245-250
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• 2001

Aminoacyl tRNA synthetases of bacteria are known as potential targets for new anti-microbial agents. To isolate new inhibitors of bacterial methionyl-tRNA synthetases from natural sources, a new target-oriented screening system using whole cells which are over-expressing a target enzyme was developed. Approximately 8,000 culture broths of microorganisms from soils were tested by this screening system. Among them, ten culture broths was found to contain inhibitory activity against methionyl -tRNA synthetases of Escherichia coli. For the validation of the screening system, this new method was compared with in vitro enzymatic method. Seven out of 10 culture broths showed inhibitory activity against methionyl-tRNA synthetases of E. coli. This result showed that the new screening system was comparable to the enzyme assay. Thus we believe that our screening system as a new method can be applied for the screening of new antibiotics inhibiting bacterial methionyl-tRNA synthetases from natural products.

• Fisheries and Aquatic Sciences
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• v.3 no.3_4
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• pp.213-216
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• 2000

The marine actinomycetes are very interesting microorganisms for finding of new antibiotics, because they are inhabited in marine environmental conditions, such as salinity, organic material and low concentration of nutrient components that are differ from those of land. In this study, the actinomycetes producing antibiotics from sea waters and bottom deposit samples collected at east coast of Korea were investigated to invent new antibiotics. Nine actinomycetes strains having the antimicrobial activity of 431 actinomycetes were selected from sea waters and bottom deposit samples. Among the 9 strains, the strain having the highest antimicrobial activity was classified to Streptomyces sp. and named Streptomyces sp. NS 13239.

• Genomics & Informatics
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• v.20 no.4
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• pp.47.1-47.13
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• 2022

Klebsiella pneumoniae is a gram-negative bacterium that is known for causing infection in nosocomial settings. As reported by the World Health Organization, carbapenem-resistant Enterobacteriaceae, a category that includes K. pneumoniae, are classified as an urgent threat, and the greatest concern is that these bacterial pathogens may acquire genetic traits that make them resistant towards antibiotics. The last class of antibiotics, carbapenems, are not able to combat these bacterial pathogens, allowing them to clonally expand antibiotic-resistant strains. Most antibiotics target essential pathways of bacterial cells; however, these targets are no longer susceptible to antibiotics. Hence, in our study, we focused on a hypothetical protein in K. pneumoniae that contains a DNA methylation protein domain, suggesting a new potential site as a drug target. DNA methylation regulates the attenuation of bacterial virulence. We integrated computational-aided drug design by using a bioinformatics approach to perform subtractive genomics, virtual screening, and fingerprint similarity search. We identified a new potential drug, koenimbine, which could be a novel antibiotic.

• Microbiology and Biotechnology Letters
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• v.18 no.6
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• pp.624-632
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• 1990

Strain 88-GT-161 producing new phthalic acid derivative and basic macrolide antibiotics was identified as being S. melanosporofuciens based on numerical taxonomic data. However, 4 unit characters among 139 units were clearly different from the common properties of 6 strains belonging to cluster No. 32 represented by the name of S. violaceoniger or S. violaceusniger, leading us to designate as a variety of S. melunosporofaciens. This paper describes the taxonomic characteristics of the strain. Isolation and chemical structures, including biological activities of the active compounds produced by this strain will be presented elsewhere.

• Journal of Microbiology and Biotechnology
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• v.15 no.2
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• pp.421-424
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• 2005

Effect of antibiotics belonging to three different groups, including third generation cephalosporins, aminoglycosides, and quinolones, on the outer membrane protein (OMP) profile of Klebsiella pneumoniae was examined. It was found that a new OMP (porins) of 40 kDa molecular mass was expressed in Klebsiella pneumoniae, when grown in the presence of ceftazidime, whereas new proteins with 30 kDa and 22 kDa masses were detected in the presence of ofloxacin. The immunoblot analysis showed that the new proteins of 40 kDa and 30 kDa molecular masses were expressed on the outer envelope, when being exposed to antibiotics ceftazidime and ofloxacin, respectively. This finding is important, as the outer surface comes in contact with the immune system, and therefore may have a bearing on the outcome of the disease.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.599-603
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• 2011

A new geldanamycin (GDM) derivative was discovered and isolated from the fermentation broth of Streptomyces hygroscopicus 17997. Its chemical structure was elucidated as thiazinogeldanamycin by LC-MS, sulfur analysis, and NMR. The addition of cysteine to the fermentation medium significantly stimulated the production level of thiazinogeldanamycin, suggesting cysteine as a precursor of thiazinogeldanamycin production. Although showing a decreased cytotoxicity against HepG2 cancer cells, thiazinogeldanamycin exhibited an improved water solubility and photostability. Thiazinogeldanamycin may represent the first natural GDM derivative characterized so far that uses GDM as its precursor. Its appearance also clearly indicates that an appropriate end-point of fermentation is of critical importance for the maximal production of GDM by Streptomyces hygroscopicus 17997.

• Fisheries and Aquatic Sciences
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• v.3 no.3_4
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• pp.217-221
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• 2000

In previous study, marine actinomycetes producing the antibiotics were investigated to invent new antibiotics from east coast of Korea. The optimum growth conditions of Streptomyces sp. NS 13239 were $28^{\circ}C$, pH 7.0 and $3\%$ of NaCl concentration in various media. Streptomyces sp. NS 13239 showed strong antimicrobial activity against gram-positive bacteria, specially Methicillin resistant Staphylococcus aureus (MRSA), but just weak antimicrobial activity against yeasts and mold. On the other hand, it did not show antimicrobial activity against gram-negative bacteria. The optimum conditions for producing antibiotics were almost consistent with optimum growth conditions except carbon source and nitrogen source.