• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.195-198
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• 2000

Production of eight avermectin components was improved in Streptomyces avermitilis wild type strain (ATCC31267) and high producing mutant strain (ATCC31780) when transformed with a foreign regulatory gene, afsR2 of Streptomyces lividans. Wild type and the high producing strain of S. avermitilis transformed with multiple copies of afsR2 improved total avermectin productions by 2.3 fold and 1.5 fold, respectively. In both of wild type and the high producing transformants carrying afsR2, glycerol was proved to be the best carbon source for the stimulation of avermectin production.

• Korean Journal of Veterinary Research
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• v.39 no.5
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• pp.896-907
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• 1999

The morphometrical characteristics such as external measurements and mandible size assessment in mice and rats have to be highly heritable and sufficiently variable between strains in order to calculate a strain specific profiles. The coat color of Korean wild rats were observed and morphometric analysis of external measurements were carried out on Korean wild rats compared to laboratory strains in order to clarify the genetic characteristics of Korean wild rats and to establish background data as a domestication of Korean wild rats for new laboratory strain. Korean wild rats were captured from Chunchon and Hoengsong. 4 inbred and 1 outbred strains of rats were used in this study for the comparison of genetic characteristic of Korean wild rats. Total body length, head length, tail length, hind foot length and ear length were measured and then statistical analysis were carried out by discrimiant analysis. The coat color of Korean wild rat showed golden white in ventral portion and dark agouti in dorsal portion. Korean wild rats could be distinguished from the other laboratory strains distinctly by morphogenetical analysis. There was significant variations among Korean wild rat compared to those of the other laboratory strains of rat. This study may provide that Korean wild rats have a unique genetic characterization compared to those of other inbred strains of rats based on morphogenetical characteristics by external measurements.

• KSBB Journal
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• v.17 no.3
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• pp.290-294
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• 2002

The present work describes the improvement of an erythritol-producing strain to lower the formation of glycerol, which is a characteristic by-product of the strain and could cause difficulties in the recovery and purification of the final product. The yeast-like fungi Moniliella suaveolens var. nigra, isolated previously in the same laboratory from beehives, was mutated by exposing it to a 4 g/L NTG solution. From a total of 2000 mutated strains, Em6j30-14 was selected as the one having the most desirable properties. Cultivating the strain for seven days in 300 mL flasks containing 30 mL of a 400 g/L glucose medium resulted in an erythritol yield of 43%. The glycerol yield was 5%, which is a value 50% lower as compared with the wild type. However, attempts to reproduce the above results in a 5L-fermenter failed, resulting in a similar erythritol concentration but a much higher formation of glycerol. Possible reasons for such a different behaviour could be oxygen limitation or the aggregation of cells, but the exact mechanism could not yet be identified. Foam formation, which is another major problem in large-scale fermentation, tended to be much lower for the mutant strain.

• Korean Journal of Microbiology
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• v.29 no.3
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• pp.160-166
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• 1991

The regulatory mechanism of tubercidin biosynthesis in Streptomyces tubercidicus was studied. In a wild type strain, addition of adenine and histidine into the medium decreased the tubercidin production by 60-65% and 40%, respectively. The effects of adenine and histidine were alleviated by the addition of inosine monophosphate and 5-aminoimidazole-4-carboxamide ribotide. The production of tubercidin in S. tubercidicus K115 strain ($ade^{-}$ ) was nearly shut off by histidine. In contrast with K115 strain, adenine inhibited the tubercidin biosynthesis in S. tubercidicus K412 strain ($his^{-}$. In S. tubercidicus F667 strain ($ade^{-}$ , $his^{-}$ ), tubercidin production was increased by adenine and histidine. From the effects of adenine and histidine on tubercidin biosynthesis in S. tubercidicus wild type and mutant strains, it became known that feedback control by adenine and histidine of biosynthetic pathwat for purine ribonucleotide and histidine are involved in the regulation of tubercidin biosynthesis.

• Mycobiology
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• v.46 no.4
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• pp.382-387
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• 2018

The entomopathogenic fungus Cordyceps militaris is a valuable medicinal ascomycete, which degenerates frequently during subsequent culture. To avoid economic losses during industrialized production, scratching stimuli of mycelia was introduced to improve the fruiting body production. The present results indicated that higher yields and biological efficiency were obtained from two degenerate strains (YN1-14 and YN2-7) but not from g38 (an insertional mutant in Rhf1 gene with higher yields and shorter growth periods). Furthermore, the growth periods of the fruiting bodies were at least 5 days earlier when the mycelia were scratched before stromata differentiation. Three ROS-scavenging genes including Cu/Zn superoxide dismutase (CmSod1), Glutathione peroxidase (CmGpx), and Catalase A (CmCat A) were isolated and their expression profiles against scratching were determined in degenerate strain YN1-14 and mutant strain g38. At day 5 after scratching, the expression level of CmGpx significantly decreased for strain g38, but that of CmSod1 significantly increased for YN1-14. These results indicated that scratching is an effective way to promote fruiting body production of degenerate strain, which may be related at least with Rhf1 and active oxygen scavenging genes.

• The Plant Pathology Journal
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• v.30 no.2
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• pp.215-219
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• 2014

The GacS/GacA two component system regulates various traits related to the biocontrol potential of plant-associated pseudomonads. The role of the sensor kinase, GacS, differs between strains in regulation of motility. In this study, we determined how a gacS mutation changed cell morphology and motility in Pseudomonas chlororaphis O6. The gacS mutant cells were elongated in stationary-phase compared to the wild type and the complemented gacS mutant, but cells did not differ in length in logarithmic phase. The gacS mutant had a two-fold increase in the number of flagella compared with the wild type strain; flagella number was restored to that of the wild type in the complemented gacS mutant. The more highly flagellated gacS mutant cells had greater swimming motilities than that of the wild type strain. Enhanced flagella formation in the gacS mutant correlated with increased expression of three genes, fleQ, fliQ and flhF, involved in flagellar formation. Expression of these genes in the complemented gacS mutant was similar to that of the wild type. These findings show that this root-colonizing pseudomonad adjusts flagella formation and cell morphology in stationary-phase using GacS as a major regulator.

• Journal of Life Science
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• v.7 no.3
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• pp.180-185
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• 1997

Methylelaiophylin generated superoxide radicals in Bacillus subtilis and showed antibacterial activity against a broad range of gram positive bacteria. The inhibition of DNA synthesis was more sensitive than one of RNA synthesis. A recombination-deficient mutant strain of B. subtilis was 2-fold more sensitive than a wild strain, and this sensitivity was reduced in the presence of an antioxidant, dithiothreitol. Methylelaiophylin generated superoxide radicals in B. subtilis lysates, and this suggests that the antibacterial activity of methylelaiophylin is related to the generation of active oxygen species in the cells.

• Mycobiology
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• v.51 no.1
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• pp.26-35
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• 2023

The diversity of A mating type in wild strains of Lentinula edodes was extensively analyzed to characterize and utilize them for developing new cultivars. One hundred twenty-three A mating type alleles, including 67 newly discovered alleles, were identified from 106 wild strains collected for the past four decades in Korea. Based on previous studies and current findings, a total of 130 A mating type alleles have been found, 124 of which were discovered from wild strains, indicating the hyper-variability of A mating type alleles of L. edodes. About half of the A mating type alleles in wild strains were found in more than two strains, whereas the other half of the alleles were found in only one strain. About 90% of A mating type combinations in dikaryotic wild strains showed a single occurrence. Geographically, diverse A mating type alleles were intensively located in the central region of the Korean peninsula, whereas only allele A17 was observed throughout Korea. We also found the conservation of the TCCCAC motif in addition to the previously reported motifs, including ATTGT, ACAAT, and GCGGAG, in the intergenic regions of A mating loci. Sequence comparison among some alleles indicated that accumulated mutation and recombination would contribute to the diversification of A mating type alleles in L. edodes. Our data support the rapid evolution of A mating locus in L. edodes, and would help to understand the characteristics of A mating loci of wild strains in Korea and help to utilize them for developing new cultivars.

• Microbiology and Biotechnology Letters
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• v.28 no.2
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• pp.63-70
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• 2000

To determine an increased acid tolerance of an adipic acid-resistant mutant Leuconostoc mesenteroides(ANaM100) developed for use as a Kimchi starter, proton permeability of cytoplasm, activities of H+-ATPase, Mg++ release and fatty acid composition of cytoplasmic membranes of strain ANaM100 were studied and compared with those of its wild type (LMw). The value of protons permeability of LMw after an acid shock at pH 5.0 was 5.4 min., while the value of ANaM100 cells was 8.4 min. at the same pH. The pH of maximal specific activ-ities of ATPase originated from the LMw and ANaM100 were 0.87 unit/mg protein at pH 6.0 and 0.92 unit/mg pro-tein at pH 5.5, respectively. The release of magnesium ion from ANaM100 was observed about 12.8% at pH 4 after 2 hours, while the wild strains of LMw released Mg++ about 27.6% under the same conditions. The content of C19:0,cyclo and C18:1 in a membrane fatty acid of ANaM100 was higher and lower, respectively than that of LMw. These results indicated that acid tolerance of adipic acid-resistant strain, ANaM100 was significantly improved in comparison with that of its wild type, LMw. In addition, the strain ANaM100 was adipic resistance based on the result of growth of the strain in comparison with that of strain LMw in a broth containing adipic acid.

• Journal of the Korean Society of Tobacco Science
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• v.15 no.1
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• pp.26-33
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• 1993

Effect of an avirulent bacteriocin-producing strain(ABPS) of Pseudomonas solanacearum adapted to low temperature on the control of tobacco bacterial wilt was examined under the natural field conditions. The ABPS of p. solanacearum were succeeding-cultured at gradually low temperature, 3$0^{\circ}C$ to 13$^{\circ}C$. The isolates adapted to low temperature grew faster than the wild type either in artificial media or on the tobacco rhizoplane. The control effect of one of the isolates on bacterial wilt was higher than that of the wild type when the bacterial suspension had been poured onto the tobacco rhizosphere soil on 1 day before and 15 days after transplanting to the field. It was suggested that ABPS of p. solanaceamm adapted to the low temperature, might be more effective biological control agent than the wild type.