• Journal of Korean Society of Environmental Engineers
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• v.30 no.8
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• pp.798-807
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• 2008

Due to economic impairment derived from metal corrosion of pumping station installed around coastal area, it was needed for related cause-effect to be investigated for understanding practical corrosion behavior and providing proper control. This research was thus carried out to determine whether the microbe can influence on metal corrosion along with its control in the laboratory. For this study, groundwater was sampled from the underground pump station(i.e. I Gas Station) where corrosion was observed. Microbial diversity on the samples were then obtained by 16S rDNA methods. From this, microbial populations showing corrosion behaviors against metals were reported as Leptothrix sp.(Iron oxidizing) and Desulfovibrio sp.(Sulfur reducing) Iron oxidizing bacteria were dominantly participating in the corrosion of iron, while sulfate reducing bacteria were more preferably producing precipitate of iron. In case of galvanized steel and stainless steel, iron oxidizing bacteria not only enhanced the corrosion, but also generated its scale of precipitate. Sulfate reducing bacteria had zinc steel corroded greater extent than that of iron oxidizing bacteria. In the inactivation test, chlorine or UV exposure could efficiently control bacterial growth. However as the inactivation intensity being increased beyond a threshold level, corrosion rate was unlikely escalated due to augmented chemical effect. It is decided that microbial corrosion could be differently taken place depending upon type of microbes or materials, although they were highly correlated. It could be efficiently retarded by given disinfection practices.

• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.111-117
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• 2018

Disinfection of ballast water using chlorine dioxide was investigated under various initial microorganism contents, dose concentrations and pH values. Kinetics of microorganism inactivation and byproduct generation of chlorine dioxide treatment were compared with the chlorine treatment. Results of treatments with chlorine dioxide concentrations of 0 to $10mg\;Cl_2/L$ showed that The optimum concentration of chlorine dioxide required for disinfection of ballast water was 1 mg/L. The difference among the second order reaction constants for bacterial disinfection at pH 7.2 to 9.2 for chlorine dioxide was less than 5% for both bacteria. This result implied that the bactericidal effects of chlorine dioxide was independent of the pH in the examined range. On the other hand, the inactivation kinetics of chlorine for E. coli and Enterococcus decreased by 17% and 25%, respectively, when pH increased from 7.2 to 9.2. The bactericidal power of chlorine dioxide was superior to sodium hypochlorite above pH 8.2, the average pH value of sea water. Furthermore, treatments of chlorine dioxide generated less harmful byproducts than chlorine and had a long-term disinfection effect on bacteria and phytoplankton from the results of experiment for 30 days. Chlorine dioxide would be a promising alternative disinfectant for ballast water.

• Journal of Microbiology and Biotechnology
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• v.13 no.1
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• pp.104-109
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• 2003

Enhancement of the production of benzoylformate reductase (BFR) was attempted under oxidative stress established by natural electron carriers. -lipoic acid (LA), flavin adenine dinucleotide (FAD), and ubiquinone (UQ) did not inhibit growth of E. faecalis when their concentrations were as high as $10{\mu}M$, while $H_2O_2$ and methyl viologen ($MV^2+$) inhibited the bacterial growth. BFR activity in the bacterial extract had increased rapidly after 1 h of cultivation after the addition of $4{\mu}M$ of natural electron carriers, and the activity was maintained during further cultivation. BFR activity of the cells treated with the natural electron carriers was $40\%$ higher than that of the control. In the presence of $4{\mu}M\;H_2O_2\;and\;MV^2+$, BFR activity increased, reaching the highest activity at about 5 h cultivation, and then decreased with further cultivation. It seems that natural electron carriers not only stimulate the induction of BFR, but also stabilize the enzyme. BFR was hardly affected by LA, FAD, and UQ, while $H_2O_2\;and\;MV^2+$ inactivated the crude enzyme. The decrease of BFR activity in the presence of $H_2O_2\;and\;MV^2+$ might be ascribed to inactivation of the enzyme by the oxidants.

• The Plant Pathology Journal
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• v.33 no.3
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• pp.276-287
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• 2017

RcsA is a positive activator of extracellular polysaccharide (EPS) synthesis in the Enterobacteriaceae. The rcsA gene of the soft rot pathogen Pantoea sp. strain PPE7 in Pleurotus eryngii was cloned by PCR amplification, and its role in EPS synthesis and virulence was investigated. The RcsA protein contains 3 highly conserved domains, and the C-terminal end of the open reading frame shared significant amino acid homology to the helix-turn-helix DNA binding motif of bacterial activator proteins. The inactivation of rcsA by insertional mutagenesis created mutants that had decreased production of EPS compared to the wild-type strain and abolished the virulence of Pantoea sp. strain PPE7 in P. eryngii. The Pantoea sp. strain PPE7 rcsA gene was shown to strongly affect the formation of the disease symptoms of a mushroom pathogen and to act as the virulence factor to cause soft rot disease in P. eryngii.

• The Korean Journal of Zoology
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• v.28 no.1
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• pp.21-30
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• 1985

By two-dimensional gel electrophoresis loss of a cell-specific protein was detected in tD strain of Amoeba proteus that had been infected by symbiotic bacteria extracted from xD strain. In 50 days of experimental infection by induced phagocytosis the host amoeba lost the ability to synthesize the tD cell-specific protein even after removal of the infective bacteria and xD cell-specific protein by growing the amoebae at $27^\\circC$. By this time the host amoebae were obligately dependent on the bacteria. From these and other results (Lorch and Jeon, Science 221:549), it is clear that the incompatibility of the infected nuclei with the cytoplasm of the uninfected amoeba and the obligate dependence of the host on bacteria are due to the irreversible inactivation or the loss of the cell-specific gene by bacterial infection in this amoeba.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.19 no.1
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• pp.11-15
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• 2013

In order to find a sanitary logistic way to handle library books, papers and environmental sources contacting the books were tested in their microbial contamination load and methods to decontaminate the books were investigated. Generally bacterial load of inner book pages was very low, but increased when contaminated with liquid such as saliva. In contrast, their lateral ends showed much higher bacterial contamination presumably due to dry dust contamination on there. As operations to improve the sanitary book conditions, turbulent air blow was found to be workable for reducing dry dusty contamination and 280 nm ultra-violet (UV) light emitting diode (LED) was so for decontaminating wet surface contamination. Microbial inactivation by the UV LED could be realized with irradiation for more than 5 minutes at 2 cm distance. Air blow of 5.5 m/s for 0.5~1 minute could reduce the dusty contamination on a model book surface.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.106-113
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• 2023

The supply of microbiological risk-free water is essential to keep food safety and public hygiene. And removal, inactivation, and destruction of microorganisms in drinking water are key for ensuring safety in the food industry. Ultraviolet-C (UV-C) irradiation is an attractive method for efficient disinfection of water without generating toxicity and adversely affecting human health. In this study, the disinfection efficiencies of UV-C irradiation on Shigella flexneri (Gram negative) and Listeria monocytogenes (Gram positive) at various concentrations in drinking water were evaluated using a water purifier. Their morphological and physiological characteristics after UV-C irradiation were observed using fluorescence microscopy and flow cytometry combined with live/dead staining. UV-C irradiation (254 nm wavelength, irradiation dose: 40 mJ/cm²) at a water flow velocity of 3.4 L/min showed disinfection ability on both bacteria up to 10⁸ CFU/4 L. And flow cytometric analysis showed different physiological shift between S. flexneri and L. monocytogenes after UV-C irradiation, but no significant shift of morphology in both bacteria. In addition, each bacterium revealed different characteristics with time-course observation after UV-C irradiation: L. monocytogenes dramatically changed its physiological feature and seemed to reach maximum damage at 4 h and then recovered, whereas S. flexneri seemed to gradually die over time. This study revealed that UV-C irradiation of water purifiers is effective in disinfecting microbial contaminants in drinking water and provides basic information on bacterial features/responses after UV-C irradiation.

• Korean Journal of Veterinary Research
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• v.12 no.1
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• pp.71-75
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• 1972

Due to the fact that an inactivated anthrax vaccine may show no or lower immunogenicity and stability, a number of spore vaccines were exclusively used worldwide. In these studies non or less allergic strain of anthrax bacillus was selected and made a capsulated vegetative organisms. Anthrax organisms of a virulent strain were cultivated on sodium bicarbonate medium with or without adding I-alanine in which B. anthracis grew luxuriantly without forming spores. Inactivation of the organisims was carried out at $37^{\circ}C$ water bath for 3 days after the bacterial culture was mixed with formalin in a final concentration of two per cent. Aluminum hydroxide gel was added to the mixture of anthrax and blackleg bacterin. Guinea pigs were injected with the vaccine via subcutaneous or intramuscular route and challenged after three weeks, and the possibilities of protection was tested. Throughout the studies, the vaccines possibly protected the vaccinated guinea pigs more than 80 per cent compared to that of the controls. This experimental results strongly suggest that the vaccine may possibly applicable to the prevention of bovine anthrax and blackleg.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.441-448
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• 2000

The production and cation flux-mediated activation of the P-type ATPase in Helicobacter pylori was investigated. Using the polymerase chain reaction (PCR), the proton pump genotype of H. pylori was found to be positive for both F-type and P-type ATPases. Yet, their production in terms of enzyme specific activity varied substantially depending on H. pylori strains, ranging over 3-fold. Its main constituent appeared to be the P-type ATPase pool, in contrast to other common bacterial compositions. Interestingly, the F-type ATPase was observed only when intact H. pyloricells were exposed to pH 4.5 or above (37$^{\circ}C$ for 1 h). In contrast, significant amounts of the P-type ATPase still remained after 1 h of cell treatment even at pH below 4.5. By enriching the acidic medium with RPMI(pH 3.0), the P-type ATPase was stabilized, accompained by inactivation of the F-type ATPase. Using H. pylori membrane vesicles, it was found that ammionia-mediated cation flux increased the rate of ATP hydrolysis by the P-type ATPase. Accordingly, these data strongly suggest that the P-type ATPase is involved or functions as an effective regulator for the cation flux across the H. pylori membrane, thereby reducing the risk of excess proton influx.

• Food Science of Animal Resources
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• v.36 no.1
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• pp.100-108
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• 2016

Microbiological contamination of eggs should be prevented in the poultry industry, as poultry is one of the major reservoirs of human Salmonella. ClO₂ gas has been reported to be an effective disinfectant in various industry fields, particularly the food industry. The aims of this study were to evaluate the antimicrobial effect of chlorine dioxide gas on two strains of Salmonella inoculated onto eggshells under various experimental conditions including concentrations, contact time, humidity, and percentage organic matter. As a result, it was shown that chlorine dioxide gas under wet conditions was more effective in inactivating Salmonella Enteritidis and Salmonella Gallinarum compared to that under dry conditions independently of the presence of organic matter (yeast extract). Under wet conditions, a greater than 4 log reduction in bacterial populations was achieved after 30 min of exposure to ClO₂ each at 20 ppm, 40 ppm, and 80 ppm against S. Enteritidis; 40 ppm and 80 ppm against S. Gallinarum. These results suggest that chlorine dioxide gas is an effective agent for controlling Salmonella, the most prevalent contaminant in the egg industry.