• Korean Journal of Microbiology
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• v.26 no.2
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• pp.82-87
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• 1988

The genetic analysis and characterization of protoplast fusion hybrids between complementary auxotrophic mutants of Candida pseudotropicalis were carried out. Nuclear fusion appeared to occur in fusion hybrids (e.g., F15 and F33), as strongly suggested by isolation of recombinants after mitotic segregation of parental genetic markers. This was confirmed by KNA content, nuclear staining and comparison of survival rate to UV light. After keeping fusion hybrids for approximately one year, the frequency of spontaneous mitotic segregation was $3.0\times 10^{-4}$ - $8.1\times 10^{-4}$ while that of induced mitotic segregation was $1.4\times 10^{-3}$- $1.7\times 10^{-3}$. These results suggested that they maintained stable karyogamy state. It was also found that the production of $\beta$-D-galactosidase from F15, F33 and F158 was somewhat increased when compared with that from either auxotrophic parents or wild type.

• Korean Journal of Microbiology
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• v.26 no.2
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• pp.113-121
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• 1988

Ozone, an atmospheric pollutant, can damage similar UV and X-rays DNA and its components. It is possible then that the KNA damage produced by this gas are similar, to some extent, to those of radiations and that they could be repaired by the same DNA repair mechanisms. It has been observed in Escherichia coli that radiosensitive strains such as lex A, rec A and pol A, all deficient to some extent for DNA repair, are more sensitive to ozone than a wild type strain. We have thendetermined the ozone resistance and host-cell reactivation of ozone-damaged T3 phages for the E. coli double mutants pol A, lex A, uvr B, lex A, uvr A, rec A and rec A lox A. According to the results, the DNA polymerase 1 plays a key role in ozone resistance and Type 11 mechanism and/or shory patch excision repair are the most important for it. The interactions between the different DNA repair mechanisms are secondary. There is a strong correlation between ozone resistance and the capacity to reactivate T3 phages damaged by ozone.

• Microbiology and Biotechnology Letters
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• v.29 no.2
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• pp.96-103
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• 2001

Phaffia rhodozyma is the most promising microbial source of astaxanthin production, though wild-type strains are needed to increase the astaxanthin content for commercial production. To increase astaxanthin content for commercial production, a mutant strain of P. rhodozyma was selected and culture conditions of the mutant selected were optimized. P. rhodozyma was treated with mutagenic agent such as NTG, acriflavine, and UV in serial order and carotenoids hyper-producing mutant strain was selected based on the capabilities of cell growth on the agar plate containing chemical inhibitors and carotenoids production. Among the mutants tested, a mutant WS-2 was finally selected. Mutant WS-2 produced 1.26mg carotenoids/g-dry cell weight and this value was about- 4-folds higher than that of wild-type. The optimum culture conditions were $24^{\circ}C$ of temperature, 1.5vvm of aeration and 300rpm of agitation. In the optimized condition, cell and carotenoids concentrations were 7.62g/l and 14.9mg/l, respectively.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.465-467
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• 2005

UIW-10 mutant obtained by UV treatment using sulfur-oxidizing bacteria, Thiobacillus sp. IW was studied. The colony size of UIW-10 was found 2 $^{\sim}$ 3 times bigger in diameter than the parent colony on TAM medium. UIW-10 mutant growth was two times higher than parent strain at 6 h culture in liquid medium containing sulfides such as sulfur and sodium thiosulfate. Initial pH and temperature for the optimum growth of UIW-10 were 6.0 and $35-40^{\circ}C$, respectively. It was found that addition of 0.5% yeast extract and 0.5 to 2.0% tryptone as nitrogen sources and the constant agitation at 150 to 200 rpm had a positive effect and the growth of UIW-10 was increased.

• BMB Reports
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• v.32 no.1
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• pp.82-85
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• 1999

The movement protein of cucumber mosaic virus (CMV) is required for cell-to-cell movement of viral RNA. The movement of viral RNA occurs through the plant intercellular connection, the plasmodesmata. The viral movement protein was known to be multi-functional. In this work, a series of deletion mutants of CMV movement protein gene were created to identify the functional domains. The mutated movement proteins were produced as inclusion body in E. coli, and purified and renatured. A polyclonal antibody was raised against the CMV-Kor strain (Korean isolate) movement protein expressed in E. coli. The ability of the truncated proteins to bind to ssRNA was assayed by UV cross-linking and gel retardation analyses. The results indicate that the domain between amino acids 118 and 160 of CMV movement protein is essential for ssRNA binding.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.224-227
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• 2002

Colistin produced from Penibacillius polymyxa was widely used as an antibiotic active against gram-negative bacteria and as feed additive. This research studied on increment of colistin productivity by mutation of P. polymyxa. As a result, several mutants were obtained from the strain by UV radiation and NTG treatment. They produced approximately 8.5${\sim}$9.0 g/L of colistin in flask and jar culture. Colistin productivity of the mutant, named Penibacillius polymyxa CBY, showed 100 times than that of wild type. When Penibacillius polymyxa CBY fermented in the optimal medium, it produced up to 18 g/L of colistin in jar fermentation.

• Journal of Microbiology and Biotechnology
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• v.2 no.2
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• pp.102-107
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• 1992

For the purpose of producing L-ornithine by microbial fermentation, mutant strains were developed from glutamate-producing bacteria by mutagenesis using N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV irradiation. Brevibacterium ketoglutamicum BK1046, a L-citrulline auxotroph which is also resistant to arginine hydroxamate (Arghx), was isolated and selected as the best producer of L-ornithine. This strain was capable of producing L-ornithine at a concentration of 24 g/l after 69 hours of cultivation in the 21 jar fermentor. The optimum supplementary level of L-arginine, a substitute for L-citrulline, was found to be about 0.2 g/l in the shake-flask fermentation.

• KSBB Journal
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• v.10 no.1
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• pp.89-96
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• 1995

An Avabidofsis thaliana gene encoding phosphoribosyl anthranilate transferase is shown to be the gene that is defective in blue fluorescent trp 1 mutant plants. This gene, named PAT1, coding region is homologous to those for the phosphoribosyl anthranilate transferase from many microorganisms. This is due to a defect in tryptophan biosynthesis that leads to an accumulation of anthranilate, a fluorescent intermediate in the tryptophan pathway. PAT1 is a single-copy gene that complements all of the visible phenotypes of the different trp1 mutants. Experiments to determine the regulation of the PAT1 gene are in progress. The wild-type PAT1 promoter and several promoter deletions of PAT1 gene have been transformed into Arabidopsis tryptophan mutants. These constructs might identify promoter elements that control this patterns. We have isolated the homozygous lines in T3 seeds and analysed the protein levels using PAT antibody and PAT protein level increased two fold in pHSl07. Finally, the potential of using PAT1 as a selectable marker or visible reporter of gene expression is being explored.

• Microbiology and Biotechnology Letters
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• v.13 no.2
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• pp.163-167
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• 1985

To investigate the condition for the protoplast fusion of Streptococcus lactis, streptomycin(200 $\mu\textrm{g}$/$m\ell$) resistant and rifampicin (200$\mu\textrm{g}$/$m\ell$) resistant mutants were isolated. By using these markers, protoplast fusion was carried out in the presence of CaCl$_2$ and polyethylene glycol. The optimal conditions for the protoplast fusion were obtained by treatment of protoplasts with 150 mM CaCl$_2$ (final concentration; 25 mM) and 40％ (w/v) PEG 4, 000 for 2 min. At the optimal conditions, the fusion frequency was 6.26$\times$10$^{-5}$ . On the other hand, genetic recombination between the antibiotic resistant mutants by mating was not observed.

• Microbiology and Biotechnology Letters
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• v.13 no.1
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• pp.79-85
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• 1985

Rhizobium japonicum wild type strains isolated from local soybean variety Jangback root nodules with higher nitrogenase activity than R. japonicum 3I1110 or 61A76 was mutangenized by N-methyl-N'-nitro-N-nitrosoguanidine and UV-irradiation, and screened by effectiveness assay with soybean. One mutant strain JB65 nodulated the roots earlier than the wild type and also expressed higher acetylene-reducing activity in the presence and absence of fixed nitrogen. The selected mutant was compared with SM35 strain and showed greater nodulation and symbiotic nitrogen fixing activity with local soybean variety Jangback than SM35 strain.