• The Plant Pathology Journal
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• v.34 no.1
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• pp.11-22
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• 2018

Type VI secretion system (T6SS) has been discovered in a variety of gram-negative bacteria as a versatile weapon to stimulate the killing of eukaryotic cells or prokaryotic competitors. Type VI secretion effectors (T6SEs) are well known as key virulence factors for important pathogenic bacteria. In many Burkholderia species, T6SS has evolved as the most complicated secretion pathway with distinguished types to translocate diverse T6SEs, suggesting their essential roles in this genus. Here we attempted to detect and characterize T6SSs and potential T6SEs in target genomes of plant-associated and environmental Burkholderia species based on computational analyses. In total, 66 potential functional T6SS clusters were found in 30 target Burkholderia bacterial genomes, of which 33% possess three or four clusters. The core proteins in each cluster were specified and phylogenetic trees of three components (i.e., TssC, TssD, TssL) were constructed to elucidate the relationship among the identified T6SS clusters. Next, we identified 322 potential T6SEs in the target genomes based on homology searches and explored the important domains conserved in effector candidates. In addition, using the screening approach based on the profile hidden Markov model (pHMM) of T6SEs that possess markers for type VI effectors (MIX motif) (MIX T6SEs), 57 revealed proteins that were not included in training datasets were recognized as novel MIX T6SE candidates from the Burkholderia species. This approach could be useful to identify potential T6SEs from other bacterial genomes.

• Journal of Korean Ophthalmic Optics Society
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• v.8 no.2
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• pp.65-69
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• 2003

The effects of grapefruit seed extract and $H_2O_2$ disinfectants on Pseudomonas aeruginosa were investigated by antimicrobial assay and scanning electron microscopy. Pseudomonas aeruginosa is a Gram negative bacteria and a common causative microorganism of bacterial keratitis. After incubation of soft contact lens in Pseudomonas aeruginosa suspension for 120 minutes containing the disinfectants, the grapefruit seed extract showed antimicrobial activity as good as the chemical disinfectant. The living rates of Pseudomonas aeruginosa in grapefruit seed extract and $H_2O_2$ disinfectants were $1{\times10^3CFU/m{\ell}$ and $0.5{\times}10^3CFU/m{\ell}$, respectively showing no major difference in the killing activity. However, the mechanisms of the antimicrobial activity were quite different as indicated by scanning electron microscopy of the bacterial surface morphology. Considering chemically or other toxins induced keratitis, the natural disinfectant isolated from grapefruit seed extract shows promising results as a soft contact lens disinfectant.

• YAKHAK HOEJI
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• v.38 no.3
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• pp.265-273
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• 1994

ln vitro and in vivo antibacterial activities of DWQ-013(1-cyclopropyl-6,8-difluoro-7-(3-methylthiomethylpyrrolidinyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid), a new fluoroquinolone antibacterial agent, were compared with those of ciprofloxacin, sparfloxacin and ofloxacin against aerobic and anaerobic standard strains and clinical isolates. DWQ-013 had a broad spectrum and potent antibacterial activity against Gram-positive and Gram-negative bacteria. The antibacterial activity of DWQ-013 against Staphylococcus aureus was equal to that of sparfloxacin(SPFX) and superior to those of ciprofloxacin(CPFX). The antibacterial activity against Gram-negative bacteria was slightly lower than those of ciprofloxacin and sparfloxacin. MIC of DWQ-013 against Pseudomonas aeruginosa$(0.781{\sim}1.563\;{\mu}g/ml)$ was usually equal to that of sparfloxacin$(0.781\;{\mu}g/ml)$ and was inferior to that of ciprofloxacin$(0.098\;{\mu}g/ml)$. The number of viable cells was decreased rapidly after addition of DWQ-013 at concentration of $1{\sim}2$ folds of MIC.

• YAKHAK HOEJI
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• v.41 no.2
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• pp.225-232
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• 1997

The in vitro antibacterial activity of DWP20367 (1-Cyclopropyl-6-fluoro-8-chloro-7-(2,7-diazabicyclo[3,3,0]oct-4-ene-7-yl)-1,4-dihydro-4-oxoquinoline-3-carboxylic acid), a new broad-spectrum fluoroquinolone, was compared with those of ciprofloxacin (CPFX), sparfloxacin (SPFX) and ofloxacin (OFLX). DWP20367 was showed antibacterial activity much higher than CPFX, SPFX and OFLK against gram-positive bacteria, while it was slightly more superior to quinolones against gram-negative bacteria. DWP20367 was particularly effective against MRSA, and its $MlC_{90}$ against clinical isolates of methicillin-susceptible S. aureus, low methicillin-resistant S. aureus and high methicillin-resistant S. aureus were 0.098, 0.781 and 1.563 micro g/ml, respectively. Against S. pneumoniae, MIC90 of DWP20367 was 2- to 8-fold higher than those of CPFX. With a view of MIC90, DWP20367 showed slightly more potent activity against P. aeruginosa and E. coli isolates than the control quinolones. DWP20367 activity was not affected by inoculum size and medium pH. But addition of $Mg^{2+}, \;Ca^{2+} $Mg2+, Ca2+ or horse serum (25%) decreased its antibacterial activity. DWP20367 was showed rapidly bactericidal activity within 2 to 4 h, and regrowth was not observed even after 24 h incubation at concentrations near the 4-fold of MIC.

• YAKHAK HOEJI
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• v.41 no.2
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• pp.233-240
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• 1997

The in vitro antibacterial activity of DWP20418 (1R, 5S, 6S)-6-[1-(R)-Hydroxyethyl)-l-methyl-2-[(2S,4S)-2-(piperazinylcarbonyl)-1-(R)-hydroxyethyl)pyrrolidine-4-thio]carb apen-2-em-3-carboxylic acid), a new carbapenem antibiotic, was compared with those of imipenem (IPM) and meropenem (MEPM). DWP20418 was comparable or slightly more superior to MEPM against gram-positive bacteria, and it showed more potent activity to IPM against gram-negative bacteria. DWP20418 was particularly active against MRSA, and its $MIC_{90}$ of methicillin-susceptible S. aureus, low methicillin-resistant S. aureus and high methicillin-resistant S. aureus were 0.391, 25 and 50 ${\mu}g/ml$, respectively. With a view of $MIC_{90}$, DWP20418 was comparable than the other carbapenems against P. aeruginosa and E. coli isolates. The activity of DWP20418 was not affected in the presence of $Mg^{2+},\;Ca^{2+}$ or horse serum. But inoculum size and alterations in pH of medium affected its antibacterial activity. DWP20418 showed rapidly bactericidal activity within 1h, and regrowth was not observed even incubation of 24hrs at the concentrations near the MIC.

• The Plant Pathology Journal
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• v.30 no.3
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• pp.245-253
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• 2014

Antimicrobial peptides (AMPs) are small but effective cationic peptides with variable length. In previous study, four hexapeptides were identified that showed antimicrobial activities against various phytopathogenic bacteria. KCM21, the most effective antimicrobial peptide, was selected for further analysis to understand its modes of action by monitoring inhibitory effects of various cations, time-dependent antimicrobial kinetics, and observing cell disruption by electron microscopy. The effects of KCM21 on Gram-negative strain, Pseudomonas syringae pv. tomato DC3000 and Gram-positive strain, Clavibacter michiganensis subsp. michiganensis were compared. Treatment with divalent cations such as $Ca^{2+}$ and $Mg^{2+}$ inhibited the bactericidal activities of KCM21 significantly against P. syringae pv. tomato DC3000. The bactericidal kinetic study showed that KCM21 killed both bacteria rapidly and the process was faster against C. michiganensis subsp. michiganensis. The electron microscopic analysis revealed that KCM21 induced the formation of micelles and blebs on the surface of P. syringae pv. tomato DC3000 cells, while it caused cell rupture against C. michiganensis subsp. michiganensis cells. The outer membrane alteration and higher sensitivity to $Ca^{2+}$ suggest that KCM21 interact with the outer membrane of P. syringae pv. tomato DC3000 cells during the process of killing, but not with C. michiganensis subsp. michiganensis cells that lack outer membrane. Considering that both strains had similar sensitivity to KCM21 in LB medium, outer membrane could not be the main target of KCM21, instead common compartments such as cytoplasmic membrane or internal macromolecules might be a possible target(s) of KCM21.

• Korean journal of food and cookery science
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• v.31 no.5
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• pp.515-523
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• 2015

In the study reported here, the antimicrobial and antioxidant activities of the ethanol leaf extract of Dendropanax morbiferus Lev. from Jeju Island was investigated. Of the 14 strains of 12 species of microorganisms tested, the extract exhibited antimicrobial activity observed against seven Gram-positive bacteria of four species, but not against six Gram-negative bacteria and a yeast strain. Using the disc diffusion method, the diameter of the inhibition zone increased with application of the extract with every strain and the highest growth inhibition was exhibited with Staphylococcus aureus KCTC 1916 at 5 mg/ml. The minimal inhibitory concentration of the extract (MIC) by turbidity was 2.5 mg/ml against Bacillus cereus KACC 12672 and 15 mg/ml when with Enterococcus faecalis KCTC 3206. The minimum bacterial concentration (MBC) values defined as being $${\geq_-}99.9%$$ reduction in viable cells against the tested strains was higher than the MIC values. Time killing curves using the optimum MIC were performed on seven strains incubated for 48 hr. The growth of B. cereus KACC 12672 was detected after 12 hr and no significant growth was found in the others strains after 48 hr (p<0.05). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity of the ethanol leaf extract was similar to that of butylated hydroxyanisole (BHA) at the same concentration. These results indicate that leaf extract of D. morbiferus Lev. can be utilized as a natural preservative and an antioxidant.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1299-1306
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• 2015

This study aims to investigate the mechanism of action of the cinnamon bark essential oil (CB), when used singly and also in combination with piperacillin, for its antimicrobial and synergistic activity against beta-lactamase TEM-1 plasmid-conferred Escherichia coli J53 R1. Viable count of bacteria for this combination of essential oil and antibiotic showed a complete killing profile at 20 h and further confirmed its synergistic effect by reducing the bacteria cell numbers. Analysis on the stability of treated cultures for cell membrane permeability by CB when tested against sodium dodecyl sulfate revealed that the bacterial cell membrane was disrupted by the essential oil. Scanning electron microscopy observation and bacterial surface charge measurement also revealed that CB causes irreversible membrane damage and reduces the bacterial surface charge. In addition, bioluminescence expression of Escherichia coli [pSB1075] and E. coli [pSB401] by CB showed reduction, indicating the possibility of the presence of quorum sensing (QS) inhibitors. Gas-chromatography and mass spectrometry of the essential oil of Cinnamomum verum showed that trans-cinnamaldehyde (72.81%), benzyl alcohol (12.5%), and eugenol (6.57%) were the major components in the essential oil. From this study, CB has the potential to reverse E. coli J53 R1 resistance to piperacillin through two pathways; modification in the permeability of the outer membrane or bacterial QS inhibition.

• THE JOURNAL OF KOREAN ORIENTAL ONCOLOGY
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• v.5 no.1
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• pp.137-150
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• 1999

Macrophage play a major role in host defence against infection and tumor development and this activity is regulated through the production of several mediators. In particular, the production of NO by macrophages mediates killing or growth inhibition of tumor cells, bacteria, fungi and parasites. However, over-expression of iNOS by various stimuli, resulting in over-production of NO, contributes to the pathogenesis of septic shock and some inflammator and auto-immune disease. Therefore, it would be valuable to develop potent and selective inhibitors of for potential therapeutic use. Thus the agent that supprees the expression of iNOS mRNA or enzyme protein will be usefull for the prevention of various diseases. We are intersted in identifying selective inhibitiors of iNOS which might be useful intreating inflammatory human diseases. In summary, we have demenstrated that scopoletin, isolated from Seman Armenicae and Radix Trichosanthis the production of NO induced by $IFN-\gammer$ plus LPS in RAW 264.7 macrophages, The mechanism for the inhibition of NO production was due to suppression of the expression of iNOS mRNA or enzyme protein.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.119.1-119.1
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• 2014

Toxic waste disposal: Many people think that when toxic waste is dumped into the ocean or into the air, it disappears. This belief is incorrect. Rather than disappearing, it accumulates over time and slowly destroys the environment. Ultimately, it leads to the destruction of human race. Plasma is environmentally friendly: Plasma is environmentally friendly because it is created and disappears. When plasma is formed on the earth, you need certain conditions such as accelerating electrons by an electrical discharge or a particle accelerator. When this is gone, plasma completely disappears, leaving no impact on the environment. Plasmas produce radicals: Even if plasma density is low at atmospheric pressure, many radicals (excited states of molecules) are created. These radicals are chemically very aggressive. So instead of using harmful chemicals, plasma can be utilized for less of an impact on the environment. Plasma can reach very high temperatures: Plasma is also useful because when you control the density, you can easily reach high temperatures up to $5000{\sim}6000^{\circ}C$ at atmosphere pressure. Because of this heat and the chemical aggressiveness of the plasma, there are many green applications for plasma technology. Pulsed power technology: Pulsed electric field for extraction, drying and killing bacteria. Treatment of biological tissue by pulsed electric fields: Extraction of substances from cells: Sterilisation, Medical applications, Growth stimulation, Food preparation. Each application has its specialities, especially with respect to pulse shape and electric field strength.