• Microbiology and Biotechnology Letters
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• v.30 no.1
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• pp.1-7
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• 2002

Phytase from Escherichia coli WC7 was purified from cell extracts and its molecular mass was estimated to be 45 kDa by SDS-PAGE. Its optimum temperature and pH for phytate hydrolysis was 6$0^{\circ}C$ and pH 5.0, respectively. The enzyme was stable up to 6$0^{\circ}C$ and over broad pH range (pH 2-12). The enzyme had higher affinity for sodium phytate than p-nitrophenylphosphate (pNPP). That is, the apparent Km value for sodium phytate and pNPP were $0.15\pm$0.02 mM and 2.82$\pm$0.05 mM, respectively. The gene encoding the phytase was cloned in E. coli XL1-Blue. Sequence analysis showed an open reading frame of 1241 Up encoding a signal peptide (22 aa) and a mature enzyme (410 aa). WC7 phytase was expressed up to 17.5 U/ml in the transformed E. coli XL1-Blue/pUEP, which was 23-fold higher than the activity from wild strain.

• Microbiology and Biotechnology Letters
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• v.31 no.4
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• pp.389-394
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• 2003

In order to screen microorganisms producing phopholipase D (PLD) had high transphosphatidylation activity, about 1,000 Actinomycetes strains were isolated from the 63 soil samples, collected over 6 local area in Korea. When the hydrolytic activity in the supernatant was determined, 131 strains produced PLD more than 0.3 U/ml. Among 131 culture broths tested, 23 ones had transphosphatidylation activity higher than 20% and finally one strain (Actinomycetes KF 923), which had highest hydrolytic and transphophadylation activity, was selected. Actinomycetes KF923 showed the highest hydrolytic activity (13 U/ml) and phosphatidylation activity (95%) after 48 h fermentation using the P medium (yeast extract 1%, peptone 1%, glucose 1.5%, glycerol 1%, $CaCo_3$ 0.4%, pH 7.2). PLD was purified from the culture broth of Actinomycetes KF923 and the specific activity of purified PLD was 567 U/mg. The molecular weight of PLD was about 55 kD and the optimum pH and temperature were 6.0 and $60^{\circ}C$, respectively. The stability of PLD toward pH and temperature were high around pH 8.0 and below $40^{\circ}C$. Special metal ions were not necessary to the PLD activity.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.457-478
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• 1992

Electrical resistance strain gauges, brittle-coatings, Moir'e fringe analysis, photoelasticity methods, etc, have been employed in the study of stress analysis and three-dimensional photoelasticity method used in this experiment. The author fabricated a total of 24 samples of maxillary and mandibular edentulous ridges with normal and sharp shapes using epoxy resin, one of the photoelastic materials. In addition, complete denture made from artificial resin teeth in other twoo sizes, large and medium size, were affixed to the specimens and attached to an articulator. The following results were attained by cutting 9 slice specimens into 6mm thick portions, in accordance with the three dimensional photoelastic stress freezing method, to analyze stress distribution status under specific static loading in the central, lateral and protrusive occlusions of the shape of edentulous ridge. 1. In the case of central occlusion, when complete resin artificial teeth in large and medium sizes were used on normal and sharp alveolar ridges, high stress distribution was broadly shown in the labio-buccal sides, and low and concentrated in the lingual sides, in all cases. Generally, the highest stresses were shown at the top of the alveolus, or at 2mm below the top of the alveolus, particularly in the specimen 2, 3, and stresses were more or less the same in the symmetrical right and left sides. 2. In the case of lateral occlusion, when the same load was applied, high stresses were shown broadly at the working sides in both the labio-buccal and lingual sides, and low and concentrated at the balanced sides. The highest stresses were shown in the top of the alveolus on the working sides in specimen 2 portion, and the lowest stresses at the balanced sides in specimen 6, slightly higher stresses were shown at retromolar parts in the balanced sides. 3. In the case of protrusive occlusion, high stresses were broadly shown at the labio-buccal sides, and slightly higher stresses at the top 2, 4, and 6mm parts of the alveolus with concentration. The highest stresses were shown in specimen No. 5 and the lowes stresses in specimen 1, 9 and stresses were more of less the same at the symmetrical right and left sides.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3315-3322
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• 2015

Staphylococcus aureus is the major causative organism of nasocomial infection being the important pathogen in the clinic. Appearance of staphylococcus aureus resistant to methicillin (MRSA) is becoming a big problem in clinics and dynamics all over the world acquiring antibiotic resistance with virulence factors as its feature differentiated from other pathogenic bacteria fast. This research intended to compare and analyze the correlation of antibiotics resistance between strains with toxin genes and distribution of toxin genes of MRSA 101 strains acquired from clinical specimen in one general hospital (enterotoxin(se), toxic shock syndrome toxin-1(tst), exfoliative toxin(et), Panton Valentine leukocidin(pvl)). seg gene, isolated the most among toxin genes, was detected in 59 strains (58.4%) and more than two toxin genes were detected in 70 strains (69.3%). As a combination possessing toxin genes, it was detected in 19 strains (18.8%) as seb, sec, seg, sei, tst and the second frequent combination was sec, seg, sei shown in 11 strains (10.9%). 19 strains (18.8%) with combinations of toxin genes same with seb, sec, seg, sei, tst had 100% resistance Ampicillin, Benzylpenicillin, Ciprofloxacin, Clindamycin, Gentamicin, Erythromycin, Telithromycin, Tetracycline antibiotics. Strains with many toxin genes showed high correlation of antibiotic resistance. Afterwards, effective therapy and thorough infection management should be preceded not to spread the resistance of MRSA strain.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.362-362
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• 2010

Today, vast attention has been paid to periodic arrays of nanostructures due to their potential for applications such as memory with huge storage density. Such application requires large-scale fabrication of well ordered nano-sized structures. One of the most widely used methods for the ordered nanostructures is lithography. This top-down process, however, has the limit to reduce size. Here the promising alternative is the self-organization of ordered nano-sized structures such as large scale 2d carbon-induced reconstructions on W(110). In the present study, we report on the first well-resolved atomic resolution STM studies of the well-known R($15{\times}3$) and R($15{\times}12$) carbon induced reconstruction of the W(110). From the atomic image of R($15{\times}3$) for different values of tunneling gap resistance, we can tell there are no missing atoms in unit cells of R($15{\times}3$) and some atomic displacements are substantial from the clean W(110), even though not all the imaged position of atoms correspond to tungsten, but may include those of carbon. We are considering two cases; First case is related to lattice deformation, or top layer of W(110) is deformed in the process of relief of strain caused by random inserting of carbon atoms possibly in the interstitial position. In the second case, R($15{\times}3$) unit cell results from a coincidence lattice between clean W(110) substrate and tungsten carbide overlayer which has rectangular atomic arrangement and giving R($15{\times}3$) coincidence lattice. beta-W2C showing rectangular unit cell should be a candidate. Further, we report on new reconstructions. Unlike the well-known R($15{\times}12$) consisting of two parts, two inner structures between two "Backbone" structures. The new reconstruction, which we found for the first time, contains more parts between the "Backbone"s. Sometimes we can observe the reconstruction consists of only inner parts without "Backbone" parts. Thus, the observed reconstruction can be built by constructing of two types of "Lego"-like block. Moreover, the rectangle shape of "Backbone" transform to parallelogram-like shape over time, the so-called wavy-R($15{\times}12$). Adsorption of hydrogen can be the reason for this transformation.

• Korean Journal of Veterinary Research
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• v.33 no.4
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• pp.623-632
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• 1993

This study was conducted to develop a sensitized latex-antigen for serodiagnosis of toxoplasmosis in animals. Tachyzoites of T gondii(RH-strain) harvested from mouse peritoneal cavity were purified through the filtraton of polycarbonate membrane(pore size, $3.0{{\mu}m}$, Costar Co.) and disrupted by ultrasonicator. The tachyzoite suspension was ultracentrifuged for 30 min at $60,000{\times}g(4{^{\circ}C})$ and the supernatant was used as a water-lysate antigen. Polystyrene latex particles of $0.8{{\mu}m}$ in diameter(Sigma) were used for the preparation of sensitized latex-antigen suspension. The several parameters including the preparation conditions, incubation buffer. serum dilution buffer and stability of agglutination reactions were evaluated and the results obtained were summarized as follows : 1. The antigen consisting of a water-lysate of T gondii tachyzoites was adsorbed onto polystyrene latex particles of $0.8{{\mu}m}$ in diameter by adding a latex suspension to an equal volume of diluted antigen solution and by incubating the mixture at $37{^{\circ}C}$ under different conditions. 2. The optimum incubation buffer used for the antigen sensitization was 0.1M Tris-HCl buffer(pH 8.0). 3. The optimum serum dilution buffer used for the latex agglutination test was 0.1M Tris-HCl-NaCl buffer(pH 7.4) containing 300 mM NaCl. But 0.1M Tris-HCl-NaCl buffer(pH 7.4) containing 300-600 mM NaCl, 0.5% BSA and 0.01% Tween-20 improved the agglutination pattems and cleared the background of microplate well without the effects on L.A titer. 4. The time required for antigen sensitization was 40 and 60 min in incubation buffer(pH 8.0) at $37{^{\circ}C}$. But the optimun time for antigen sensitization was min at $37{^{\circ}C}$. 5. The optimun quantity of antigen absorbed on latex particles for proper agglutination was the range of 20 to $32{\mu}g$ of latex particles. 6. The optimun concentration of the latex-antigen suspension for the proper agglutination reaction was determined as 0.2%(w/v). 7. The specificity, rapidity and simplicity of the latex-particle agglutination test suggested that it might be adaptable to large scale serum screening.

• Korean Journal of Microbiology
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• v.54 no.3
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• pp.200-207
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• 2018

At high salt concentration, glycine betaine is transported into Bacillus subtilis and growing rate of the cell is not suppressed. Also according to recent studies, cell growth is maintained normal growth rate at low temperature. Low temperature results in a stress response of Bacillus subtilis that is characterized by strong repression of major metabolic activities such as translation machinery and membrane transport. In this regards, genes showing cold sensitive phenotype are cold-induced DEAD box RNA helicases (ydbR, yqfR) and fatty acid desaturases (bkdR, des). Therefore to understand the effect of glycine betaine on cold growth of Bacillus subtilis, we investigated the effect of glycine betaine on growth rate of these deletion mutants showing cold sensitive phenotype. Glycine betaine strongly stimulated growth of wild type Bacillus subtilis JH642 and deletion mutants of ydbR and yqfR at $20^{\circ}C$ (190~686 min $T_d$ difference). On the other hands, glycine betaine does not show growth promoting effects on deletion mutants of bkdR, and des at cold conditions. Same cold protectant growth results were shown with the precursor choline instead of glycine betaine. We investigated the effects of detergents on the cell membrane in bkdR and des deficient strains associated with cell membrane. It was identified that bkdR deficient strain shows retarded growth with detergent such as Triton X-100 or N-lauryl sarcosine compared with wild type cell. Thus, it is possible that deletion mutation of bkdR modifies membrane structure and effects on transport of glycine betaine.

• Journal of Life Science
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• v.22 no.3
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• pp.417-427
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• 2012

We compared the transcriptome in response to propanol stress in wild-type and propanol-resistant mutant Escherichia coli using the DNA microarray technique. The correlation value of RNA expression between the propanol-treated wild type and the untreated-one was about 0.949, and 50 genes were differentially expressed by more than twofold in both samples. The correlation value of RNA expression between the propanol-treated mutant and the untreated one was about 0.951, and 71 genes in two samples showed differential expression patterns. However, the values between the wild type and mutant, regardless of propanol addition, were 0.974-0.992 and only 1-2 genes were differentially expressed in the two strains. The representative characteristics among differentially expressed genes in W3110 or P19 treated with propanol compared to untreated samples were up-regulation of hest shock response genes and down-regulation of genes relating to ribosome biosynthesis. In addition, many genes were regulated by transcription regulation factors such as ArcA, CRP, FNR, H-NS, GatR, or PurR and overexpressed by sigma factor RpoH. We confirmed that RpoH mediated an important host defense function in propanol stress in E. coli W3110 and P19 by comparison of cell growth rate among the wild type, rpoH disruptant mutant, and rpoH-complemented strain.

• Journal of Life Science
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• v.15 no.6 s.73
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• pp.1005-1012
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• 2005

Endophytic Bacillus sp. CY22 was previously isolated from the interior of balloon flower root and showed strong antifungal activity against phytopathogenic fungi such as Rhizoctonia solnni, Fusarium oxysporum, and Phythium ultimum. Many Bacillus strains produce antifungal compound such as iturin, fengycin, and mycosubtilin. We isolated and identified antifungal compound from cell supernatant of the endophytic strain. By the MALDI-TOF mass result, the antifungal compound was similar to the known antifungal lipopeptide iturin. It was found that the purified iturin had three isoforms with protonated masses of m/z 1,043.39, 1,057.42, and 1,071.42 and different structures in combination with $Na^{+}$ ion using MALDI-TOF MS. The ita22 gene, which transacylase gene is associated with production of antifungal iturin, had an open reading frame (ORF) of 1,200 bp encoding 400 amino acids. Results of deduced amino acids sequence homology search, Ita22 was homologous with FenF (BAB69697) of Bacillus subtilis 168.

• Journal of Life Science
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• v.13 no.4
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• pp.421-427
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• 2003

A natural habit at bacterium, Enterobacter intermedious KH410 was isolated from freshwater plant root and identified. Adsorption of heavy metals such as lead, cadmium, and copper by this strain was examined. The minimal inhibitory concentrations(MIC) for each metal were 1.78 mM for lead, 0.17 mM for cadmium and 1.39 mM for lopper, respectively. Maximum production of dried cell was 2.56 g/$\ell$ in LB medium containing 0.5% NaCl, 1% yeast extract and 1% of lactose. Optimal conditions for adsorption were 0.6 dry g-biomass, at pH 4.0 and the temperature of $20^{\circ}C$. Adsorption equilibrium reached maximum after 30 min in 400 mg/$\ell$ metal solution. The adsorption capacity (K) of copper was 1.5 times higher than that of cadmium and lead was 1.1 times higher than that of cadmium. from the results obtained in this study, Freundlich adsorption model was applicable for all metals. Adsorption strength (1/n) of heavy metal ions were in the order of cadmium>copper>lead. The adsorption of dried cell for lead, cadmium, and copper was 56.2, 58.0, 55.8 mg/g-biomass, respectively. Pretreatment to increase ion strength was the most effective with 0.1 M NaOH whereas slight difference was found both KOH and $CaCl_2$ upon same concentration. Effective desorption was induced by 0.1 M EDTA for lead and 0.1 M $HNO_2$ for cadmium and copper.