• Journal of Microbiology
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• v.37 no.3
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• pp.180-184
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• 1999

hybridoma cells producing IgM anti-pneuococcal 6B polysaccharide antibodies were induced to switch to IgG-producing cells in vitro by treating with acridine orange. Treating 0.5 $\mu\textrm{g}$/ml of acridine orange for 24 hours generated maximal number of variant cells. The maximal isotype switch frequency was 3${\times}$10-5, which is about 30-fold higher than the frequency of spontaneous switching. Resulting IgG-producing variants were enriched by sib selection and ELISA spot assay. Two IgG3-producing variant cells were finally cloned by limiting dilution. The variant cells produced similar amounts of antibodies as their parental cells did. The two switched antibodies had similar reactivity to pneumococcal 6B polysaccharide. When compared to their parental IgM antibodies, the switched IgG3 than that of IgM antibody. The antibodies will be useful as essential tools for comparative study of the role of heavy chain isotypes in protection against Streptococcus pneumoniae.

• Korean Journal of Microbiology
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• v.30 no.1
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• pp.60-64
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• 1992

The secretion vector with promoter and signal sequence region of neutral protease gene (npr) from Bacillus amyloliquefaciens was constructed by the technique of polymerase chain reaction (PCR). A unique restriction iste was introduced into the 3' of the signal coding region by the synthesis of PCR primer. To demonstrate the function of cloned promoter and signal sequence, we used the E. coli .betha.-lactamase structural gene as a foreign gene. The signal sequence of .betha.-lactamase gene was deleted by Bal31 exonuclease and only mature region was introduced into the secretion vector. Bacillus subtilis cells transformed by the recombinant vector synthesized the fusion protein and were also capable of removing the signal peptide from the original fusion protein, as judged by the assay of .betha.-lactamase activity and secretion into the growth medium by western blotting.

• The Microorganisms and Industry
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• v.16 no.1
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• pp.7-17
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• 1990

In summary, the nature of the amino acid changes that impart oncogenicity in either the focus formation or tumorigenicity assay can be inferred by analysis of PCR-amplified DNA from tumor-derived NIH3T3 transformants and confirmed by analysis of primary liver tumors. Putative activating mutations in the c-K-ras genetic locus have been shown to involve a single-base modification of either G-C base pair at codon 12 leading to aspartate or cystein substitutions for glycine. The oncogenicity of an N-ras oncogene containing the N-ras C gene region may be related to an amino acid substitution of valine for glycine at codon 13.

• Korean Journal of Microbiology
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• v.16 no.4
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• pp.161-169
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• 1978

Escherichiae-like organisms were isolated from rectal specimens of 56 children who were either in preschool age or in elementary school. The isolated strains were subjected to tests to screen enteropathogens producing heat-labile enterotoxin and susceptibility test to various antibiotics by disc diffusion method on agar plates. Production of heat-labile enterotoxin by the strains was assyed in the sensitive and reproducible cultured adrenal tumor cell system. The assay was sterodogenesis of the cell in the presence of heat-labile enterotoxin. Among 56 strains, gave positive reaction in the test of toxin production. This meant that about 10% of the children population objected to the study harbored the toxigenic strain of enteropathogenes. Some of these toxigenic strains were resistant to the antibiotics employed in the test. This study suggested that considerable population in Korea may harbor entertoxigenic E. coli as a part of intestinal normal flora. The toxigenic strains which are resistant to antibiotics may bring issue of public health in the future.

• Journal of Pharmaceutical Investigation
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• v.14 no.4
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• pp.189-194
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• 1984

The present study was undertaken to evaluate the relative bioavailability of doxycycline hyclate and doxycycline-L-methylenelysine, a new synthetic derivative of doxycycline. Single doses, equivalent to 100mg of doxycycline hyclate, were administered orally to 10 healthy male volunteers. Serum concentrations were determined periodically over 12 hrs. by microbiological assay. Peak serum concentrations were reached within 4 hrs. Doxycycline hyclate $(1.38mcg.ml^{-1})$ gave 1.66 tines higher concentration than doxycycline-L-methylenelysine $(0.38mcg.\;ml^{-1})$. And the areas under the serum concentrationtime curves 0 to 12 hrs were $8.38mcg.hr.ml^{-1}$ (doxycycline hyclate) and $5.56mg\;hr.ml^{-1}$(doxycycline).

• Journal of Microbiology
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• v.35 no.1
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• pp.10-14
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• 1997

The database of metabolic fingerprints generated using the GIolog system of lactic acid bacteria isolated from kimchi, described by Lee et al. (8), was used for the identification of 75 Leuconostoc isolates. The test strains were isoalted using a selective isolation medium specific for the genus Leuconostoc and examined for their ability to oxidize carbon sources using the Biolog system. The results show that the 75 test strains were identified to the known Leuconostoce clusters. It is suggested that the Biolog system can be applied for rapid identification of lactic acid bacteria isolated from kimchi.

• Korean Journal of Microbiology
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• v.27 no.3
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• pp.259-264
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• 1989

The adherence of $^{3}H$-labeled oral streptococcal cells to protein-coated hydroxyapatite (HA) beads was studied by a standard adherence assay. The adherence equilibrium for S. mutans 10449 occured in about 2 hrs. The cell numbers adhering to SHA was 50% less than those on bare HA. Sailva from different subjects had varying effect on bacterial adherence. The use of saliva adsorbed with homologouis bacteria decreased S. mutans adherence by 38% ; this indicates the presence of salivary agglutinin in acquired pellicle formed on HA. Animal sera and BSA decreased S. sanguis adherence. BSA concentration as high as 10mg/ml caused up to 87% adherence inhibition. The desorption experiment of adhered bacteria confirmed the previous reports that the adhesive sites on HA beads for S. mutans were different from those for S. sanguis and that S. mutans could enhance the adherence of S. sanguis but not vice versa.

• Journal of Microbiology
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• v.45 no.4
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• pp.297-304
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• 2007

The detection of virulence factors of Aeromonas is a key component in determining potential pathogenicity because these factors act multifunctionally and multifactorially. In this study water samples were collected from a trout farm on a seasonal basis, and diseased fish and Aeromonas species were isolated and identified. For rapid detection of six virulence factors of isolated Aeromonas, a hexaplex-polymerase chain reaction (hexaplex-PCR) assay was used. The detected virulence factors include aerolysin (aer), GCAT (gcat), serine protease (ser), nuclease (nuc) lipase (lip) and lateral flagella (laf). The dominant strain found in our isolates was Aeromonas sobria, and the dominant virulence factors were aer and nuc for all seasons. We confirmed that A. sobria and two of the virulence genes (aer and nuc) are related. We proposed a method by which one can identify the major strains of Aeromonas: A. hydrophila, A. sobria, A. caviae, and A. veronii, using hexaplex-PCR.

• Korean Journal of Microbiology
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• v.23 no.4
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• pp.271-281
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• 1985

Bacillus thuringiensis var. thuringiensis produces an extracellular insecticidal thermostable .betha.-exotoxin, which was purified through microfiltering, barium precipitation, charcoal absorption chromatography, ion exchange column chromatography and gel filtration. The exotoxin in each purification step was detedted by thin layer chromatography, high pressure liquid chromatography and paper electrophoresis with efficient results. The exotoxin productivity on time course was checked by spectrophotometric absorbance at 258nm with the result that the exotoxin was initially produced in 6 hour culture and reached maximum value in 36 hour culture. Anti-bacterial effect test on Micrococcus flava was applied as toxicity test. The results showed that frowth inhibition of M. flava could be shown in plate assay of cell free filtered supernatant, alkaline eluant from charcoal and purified exotosin obtained from gel filtration column chromatography on Sephadex G-10 appeared to be 740. Heat stability of the exotoxin was confirmed through autoclaving twice.

• Journal of Microbiology
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• v.41 no.4
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• pp.320-326
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• 2003

In order to identify Vibrio vulnificus in the Yellow Sea near Gunsan, Korea during the early and late summers, the efficiency of the real-time quantitative TaqMan PCR was compared to the efficiency of the conventional PCR and Biolog identification system^TM. Primers and a probe were designed from the hemolysin/cytolysin gene sequence of V. vulnificus strains. The number of positive detections by real-time quantitative TaqMan PCR, conventional PCR, and the Biolog identification system from seawater were 53 (36.8%), 36 (25%), and 10 strains (6.9%), respectively, among 144 samples collected from Yellow Sea near Gunsan, Korea. Thus, the detection method of the real-time quantitative TaqMan PCR assay was more effective in terms of accuracy than that of the conventional PCR and Biolog system. Therefore, our results showed that the real-time TaqMan probe and the primer set developed in this study can be applied successfully as a rapid screening tool for the detection of V. vulnificus.