• Journal of Ginseng Research
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• v.18 no.3
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• pp.175-181
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• 1994

We studied the folilar wiping effects of antioxidants (ascorbate, glutathione and sodium azide), which effectively inhibited the chlorophyll bleaching or completely recorved the early stage of photosynthesis of Panax ginseng C.A. Meyer, on photosynthesis, stomatal resistance, free sugar, starch, and total saponin contents of ginseng under the excess light intensity (45 kLux) during 6 days. Ascorbate and glutathione, endogenous antioxidant, recovered photosynehtsis and stomatal resistance, and reduced the photoinhibition by the excess light intensity (45 kLux) on free sugar, starch and total saponin contents. But sodium azide, exogenous $^{1}O_2$ quencher, showed negative effect. Therefore, we assumed that carbohydrates and saponin metabolisms of ginseng by antioxidants (ascorbate, glutathione) were normal. For the reduction of inhibition by excess light in ginseng a program for the higher activation of antioxidants and antioxidative enzymes in ginseng leaf will be desirable. Key words Antioxidants, ascorbate, glutathione, Photoinhibition, ginseng.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.6
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• pp.516-521
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• 2006

The use of gltA gene, as a new biomarker for environmental stress biomonitoring, was investigated because of its key position as the first enzyme of the tricarboxylic acid (TCA) cycle. A recombinant bioluminescent Escherichia coli strain, EBJM2, was constructed using a plasmid carrying the citrate synthase (gltA) promoter transcribing the Photorhabdus luminescens IuxCDABE genes (gltA::luxCDABE). The responses from this strain were studied with five different classes of toxicants: DNA damage chemicals, phenolics, oxidative-stress chemicals, PAHs, and organic solvents. EBJM2 responded strongly to DNA damage chemicals, such as mitomycin C (MMC) and methyl-nitro-nitrosoguanidine (MNNG) and nalidixic acid with the strongest responses. In contrast, tests with several compounds from the other four classes of toxicants gave no significant response. Therefore, EBJM2 was found to be sensitive to DNA damage chemicals.

• Journal of Microbiology and Biotechnology
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• v.17 no.8
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• pp.1254-1261
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• 2007

In the present study, we have constructed a bioluminescent bioreporter for the assessment of nitrate/nitrite bioavailability in wastewater. Specifically, an approximately 500-bp DNA fragment containing a nitrate/nitrite-activated nasR-like promoter (regulating expression of genes encoding nitrite reductase in the genus Klebsiella) was fused upstream of the Vibrio fischeri luxCDABE gene cassette in a modified mini-Tn5 vector. Characterization of this strain, designated W6-1, yielded dose-dependent increased bioluminescence coincident with increased nitrate, nitrite, and ammonium added to the growth medium from 1 to 11 ppm. Bioluminescence in response to nitrogen species addition was light dependent up to 10, 7, and 8 ppm with nitrate, nitrite, and ammonium, respectively. This response was linear in the range from 1 to 8 ppm for nitrate ($R^2=0.98$), 1 to 6 ppm for nitrite ($R^2=0.99$), and 1 to 7 ppm for ammonium ($R^2=0.99$). A significant bioluminescent response was also recorded when strain W6-1 was incubated with slurries from aged, nitrate/nitrite contaminated wastewater. Thus, bioreporter strain W6-1 can be used to elucidate factors that constrain the use of nitrate/nitrite in wastewaters.

• Journal of Microbiology and Biotechnology
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• v.24 no.12
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• pp.1609-1621
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• 2014

The plant pathogen Burkholderia gladioli, which has a broad host range that includes rice and onion, causes bacterial panicle blight and sheath rot. Based on the complete genome sequence of B. gladioli BSR3 isolated from infected rice sheaths, the genome of B. gladioli BSR3 contains the luxI/luxR family of genes. Members of this family encode N-acyl-homoserine lactone (AHL) quorum sensing (QS) signal synthase and the LuxR-family AHL signal receptor, which are similar to B. glumae BGR1. In B. glumae, QS has been shown to play pivotal roles in many bacterial behaviors. In this study, we compared the QS-dependent gene expression between B. gladioli BSR3 and a QS-defective B. gladioli BSR3 mutant in two different culture states (10 and 24 h after incubation, corresponding to an exponential phase and a stationary phase) using RNA sequencing (RNA-seq). RNA-seq analyses including gene ontology and pathway enrichment revealed that the B. gladioli BSR3 QS system regulates genes related to motility, toxin production, and oxalogenesis, which were previously reported in B. glumae. Moreover, the uncharacterized polyketide biosynthesis is activated by QS, which was not detected in B. glumae. Thus, we observed not only common QS-dependent genes between B. glumae BGR1 and B. gladioli BSR3, but also unique QS-dependent genes in B. gladioli BSR3.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.6
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• pp.48-56
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• 1989

Contact-type linear image sensors for facsimile have been fabricated by means of rf glow discharge decomposition method of silane. The dependence of their electrical and optical properties on rf power, $SiH_4$ flow rate, ambient gas pressure, $H_2SiH_4$ ratio and substrate temperature are described. The a-Si:H monolayer demonstriated photosensitivity of 0.85 and $I_{ph}/I_d$ ratio of 100 unger 100 lux illumination. However, this monolayer has relatively high dark current due to carrier injection from both electrodes, resulting in low $I_{ph}/I_{dd}$ ratio. To suppress the dark current we have fabricated $SiO_2/i-a-Si:H/p-a-Si:H:B$ multilayer film with blocking structure. The photocurrent of this multilayer sensor with 6 V bias became saturated ar about 20nA under 10 lux illumination, while the dark current was less than 0.2 nA. Moreover, the spectral sensitivity of the multilayer film was enhanced for short wavelength visible region, compared with that of the a-Si:H monolayer. These results show that the fabricated photocon-ductive film can be used as the linear image sensor of the facsimile.

• Journal of the Korean Home Economics Association
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• v.35 no.3
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• pp.193-204
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• 1997

The purpose of this study is to measure some physical environmental factors and to doucument students' perceptions of them. 11 middle schools in Cheju City were divided into four areas according to their locations and two schools were selected for the study. 144 thirteen-year-old students in two middle school in a overcrowded area in Cheju City-one middle school building is insulated and the other is not insulated-were taken for the questionnaire survey. The finding of the study are as follows: 1) The classrooms were not equipped with any heating equipment. The buildings are not insulated well. As a result, the room temperature was much lower(12.9-16.2℃) than comfortable indoor temperature in winter(21.5-24.5℃). The classroom were found to be colder(12.9-16.2℃) than usual pleasant indoor temperature(21.5-24.5℃) in winter. 2) The classroom were so far from the street(20m) that there was little noise from traffic. Nevertheless, the noise level was higher(62.5-66.2 dB(A), when the windows were open; 51.7-62.8dB(A), when closed than the noise tolerance level specified in the Environment Protection Laws(50.0dB(A)). 3) As for the visual environment, the location of classroom, the adequate sun exposure, and the total states of windows in classrooms influenced on the illuminance. While standard indoor illuminance is 300 Lux, the classrooms facing south had illuminance of 231 Lux, from day light: and the ones facing west, 380 Lux. 4) Students generally found other aspects of the physical environment of their classrooms unsatisfactory. Chalk dust was generated to a serious extent near the main chalkboard(0.25mg/㎥) of classrooms.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.5
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• pp.475-481
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• 2000

The growth of the microalgal Spiulina platensis in a batch photobioreactor had been studied to determine the influence of temperature, light intensity, and culture medium on the growth and c-phycocyanin content of the biomass. The most favorable conditions for high biomass and c-phycocyanin production were as follows: light intensity of 3500 lux, temperature of $35^{\circ}C,\;NaHCO_3\;of\;1.0{\%}$ for pH control, $0.2{\~}0.3{\%}\;Na_2CO_3$ for carbon source, and $0.2{\~}0.3{\%}\;NaCO_3$ for nitrogen source. The c-phycocyanin and chlorophyll content on most favorable condition were about $11{\%},\;1.0{\%}$, respectively.

• Journal of Microbiology
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• v.44 no.2
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• pp.226-232
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• 2006

Swarming has proven to be a good in vitro model for bacterial surface adherence and colonization, and the swarming differentiation of a bacterium has been shown to be coupled with changes in the expression of virulence factors associated with its invasiveness, particularly in the early stages of infection. In this study, we attempted to determine whether the expression of vvhA, which encodes for hemolysin/cytolysin (VvhA), is either upregulated or downregulated during the swarming differentiation of V. vulnificus. The insertional inactivation of vvhA itself exerted no detectable effect on the expression of V. vulnificus swarming motility. However, in our lacZ-fused vvhA transcriptional reporter assay, vvhA expression decreased in swarming V. vulnificus as compared to non-swarming or planktonic V. vulnificus. The reduced expression of vvhA in swarming V. vulnificus increased as a result of the deletional inactivation of luxS, a gene associated with quorum sensing. These results show that vvhA expression in swarming V. vulnificus is downregulated via the activity of the LuxS quorum-sensing system, suggesting that VvhA performs no essential role in the invasiveness of V. vulnificus via the adherence to and colonization on the body surfaces required in the early stages of the infection. However, VvhA may playa significant role in the pathophysiological deterioration occurring after swarming V. vulnificus is differentiated into planktonic V. vulnificus.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1390-1400
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• 2015

Quorum sensing is a process of cell-to-cell communication in which bacteria produce autoinducers as signaling molecules to sense cell density and coordinate gene expression. In the present study, a LuxI-type synthase, AnoI, and a LuxR-type regulator, AnoR, were identified in Acinetobacter nosocomialis, an important nosocomial pathogen, by sequence analysis of the bacterial genome. We found that N-(3-hydroxy-dodecanoyl)- _L -homoserine lactone (OH-dDHL) is a quorum-sensing signal in A. nosocomialis. The anoI gene deletion was responsible for the impairment in the production of OH-dDHL. The expression of anoI was almost abolished in the anoR mutant. These results indicate that AnoI is essential for the production of OH-dDHL in A. nosocomialis, and its expression is positively regulated by AnoR. Moreover, the anoR mutant exhibited deficiency in biofilm formation. In particular, motility of the anoR mutant was consistently and significantly abolished compared with that of the wild type. The deficiency in the biofilm formation and motility of the anoR mutant was significantly restored by a functional anoR, indicating that AnoR plays important roles in the biofilm formation and motility. Furthermore, the present study showed that virstatin exerts its effects on the reduction of biofilm formation and motility by inhibiting the expression of anoR. Consequently, the combined results suggest that AnoIR is a quorum-sensing system that plays important roles in the biofilm formation and motility of A. nosocomialis, and virstatin is an inhibitor of the expression of anoR.

• Journal of Microbiology and Biotechnology
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• v.32 no.9
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• pp.1134-1145
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• 2022

SCO6993 (606 amino acids) in Streptomyces coelicolor belongs to the large ATP-binding regulators of the LuxR family regulators having one DNA-binding motif. Our previous findings predicted that SCO6993 may suppress the production of pigmented antibiotics, actinorhodin, and undecylprodigiosin, in S. coelicolor, resulting in the characterization of its properties at the molecular level. SCO6993-disruptant, S. coelicolor ΔSCO6993 produced excess pigments in R2YE plates as early as the third day of culture and showed 9.0-fold and 1.8-fold increased production of actinorhodin and undecylprodigiosin in R2YE broth, respectively, compared with that by the wild strain and S. coelicolor ΔSCO6993/SCO6993⁺. Real-time polymerase chain reaction analysis showed that the transcription of actA and actII-ORF4 in the actinorhodin biosynthetic gene cluster and that of redD and redQ in the undecylprodigiosin biosynthetic gene cluster were significantly increased by SCO6993-disruptant. Electrophoretic mobility shift assay and DNase footprinting analysis confirmed that SCO6993 protein could bind only to the promoters of pathway-specific transcriptional activator genes, actII-ORF4 and redD, and a specific palindromic sequence is essential for SCO6993 binding. Moreover, SCO6993 bound to two palindromic sequences on its promoter region. These results indicate that SCO6993 suppresses the expression of other biosynthetic genes in the cluster by repressing the transcription of actII-ORF4 and redD and consequently negatively regulating antibiotic production.