• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1119-1128
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• 2015

1-Aminocyclopropane-1-carboxylate (ACC) deaminase, which is encoded by some bacteria, can reduce the amount of ethylene, a root elongation inhibitor, and stimulate the growth of plants under various environmental stresses. The presence of ACC deaminase activity and the regulation of ACC in several rhizospheric bacteria have been reported. The nitrogen-fixing Pseudomonas stutzeri A1501 is capable of endophytic association with rice plants and promotes the growth of rice. However, the functional identification of ACC deaminase has not been performed. In this study, the proposed effect of ACC deaminase in P. stutzeri A1501 was investigated. Genome mining showed that P. stutzeri A1501 carries a single gene encoding ACC deaminase, designated acdS. The acdS mutant was devoid of ACC deaminase activity and was less resistant to NaCl and NiCl₂ compared with the wild-type. Furthermore, inactivation of acdS greatly impaired its nitrogenase activity under salt stress conditions. It was also observed that mutation of the acdS gene led to loss of the ability to promote the growth of rice under salt or heavy metal stress. Taken together, this study illustrates the essential role of ACC deaminase, not only in enhancing the salt or heavy metal tolerance of bacteria but also in improving the growth of plants, and provides a theoretical basis for studying the interaction between plant growth-promoting rhizobacteria and plants.

• Korean Journal of Environmental Agriculture
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• v.36 no.3
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• pp.217-221
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• 2017

BACKGROUND: For the food safety of cultivated mushroom, information on the safety of agricultural by-products imported as medium substrates for mushroom cultivation is urgently needed. Therefore, this study was performed to detect the presence of heavy metals, residual pesticides, and nutrient component in the imported medium substrates. METHODS AND RESULTS: Six kinds of medium substrates imported from nine countries from 2015 to 2017 were investigated. A mercury analyzer MA-2000 and an inductively coupled plasma spectrometer OPTIMA 7000DV were used to analyze mercury, lead, arsenic, copper, nickel and cadmium. All of these heavy metals were detected at lower level than heavy metal tolerance standard level of by-product fertilizer in Korea. When 246 kinds of residual pesticides were examined by GC and HPLC, imidacloprid, thiamethoxam and carbendazim were detected from Egyptian beet pulp, Indian cottonseed meal and cottonseed hull, respectively. The content of nutrient components (water, crude ash, crude fat, crude protein and crude fiber) varied among imported countries and the medium substrates. CONCLUSION:The presence of heavy metals and residual pesticides in imported medium substrates for mushroom cultivation was confirmed. For the safe production of mushroom, this study shows that imported medium materials for mushroom cultivation need to be managed through continuous monitoring.

• Economic and Environmental Geology
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• v.42 no.5
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• pp.427-434
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• 2009

Indigenous bacterium which shows a tolerance to high metal toxicity was isolated from soil concomitantly contaminated with oil and heavy metals. The characteristics of the bacterium for Pb and Cd biosorption was investigated under the various experimental conditions such as bacterial growth phase, the initial metal concentration, the input biomass amount, temperature and pH. The Langmuir adsorption isotherm modeling was described to know the capacity and intensity of biosorption. The low initial concentration of heavy metals and high biomass has a maximum heavy metal removal efficiency, but biosorption capacity of Pb and Cd has different values. Biosorption efficiency was highest in the end of the microbial growth stage and under pH 5~9 condition, but was less affected by temperature variation of 25~$35^{\circ}C$. The maximum biosorption capacity for Pb and Cd was 62.11 and 192.31 mg/g, respectively and each $R^2$ was calculated as 0.71 and 0.98 by applying Langmuir isothermal adsorption equation. Biosorption for Cd was considered as monomolecular adsorption to single layer on the surface of cells, whereas biosorption for Pb was considered as accumulation process into the cell by the microbial metabolism and precipitation reaction with anion of bacteria.

• Economic and Environmental Geology
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• v.36 no.4
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• pp.275-284
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• 2003

We collected the samples of stream sediments from primary channels in order to establish natural background of major and minor elements for geologic units in the Gurye area. Stream sediments samples having no possibility of contamination effect and representing drainage basins composed of uniform geology, were collected from April to May in 1999, the chemical analysis of which was carried out. The tolerable level was used to investigate the enrichment degree of harmful elements. The contents of Ni and Cr exceeded the tolerance level in some sections. The tolerance level excess of those elements was regarded as the effect of the metamorphic rock which constituted the bed rock of the area. In order to identify the comprehensive enrichment pattern, the tolerable level was used in calculating the enrichment index. The enrichment index of harmful heavy metals showed that Granite gneiss area is 0.39, Porphyroblastic granite gneiss area 0.32, Biotite gneiss area 0.42, Migmatitic gneiss area 0.41, Tuff area 0.30, Andesite area 0.46, Conglomerate area 0.42, and Granite area 0.26. Those results showed that natural background of Gurye area had not been exposed to harmful heavy metal elements.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.294-294
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• 2010

Over the last decade, dye-sensitized solar cell (DSSC) has attracted much attention due to the high solar-to-electricity conversion efficiency up to 10% as well as low cost compared with p-n junction photovoltaic devices. DSSC is composed of mesoporous TiO2 nanoparticle electrodes coated with photo-sensitized dye, the redox electrolyte and the metal counter electrode. The performances of DSSC are dependent on constituent materials and interface as well as device structure. Replacing the heavy glass substrate with plastic materials is crucial to enlarge DSSC applications for the competition with inorganic based thin film photovoltaic devices. One of the biggest problems with plastic substrates is their low-temperature tolerance, which makes sintering of the photoelectrode films impossible. Therefore, the most important step toward the low-temperature DSSC fabrication is how to enhance interparticle connection at the temperature lower than $150^{\circ}C$. In this talk, the key issues for high efficiency plastic solar cells will be discussed, and several strategies for the improvement of interconnection of nanoparticles and bendability will also be proposed.

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.04a
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• pp.24-24
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• 2018

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.675-680
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• 2006

This is a study of fatigue strength of weld deposits with transverse cracks in plate up to 50 mm thick. It is concerned with the fatigue properties of welds already with transverse cracks. A previous study of transverse crack occurrence, location and microstructure in accordance with welding conditions was published in the Welding Journal (Lee et al., 1998). A fatigue crack develops as a result of stress concentration and extends with each load cycle until fatigue occurs, or until the cyclic loads are transferred to redundant members. The fatigue performance of a member is more dependent on the localized state of stress than the static strength of the base metal or the weld metal. Fatigue specimens were machined to have transverse cracks located on the surface and inside the specimen. Evaluation of fatigue strength depending on location of transverse cracks was then performed. When transverse cracks were propagated in a quarter-or half-circle shape, the specimen broke at low cycle in the presence of a surface crack. However, when the crack was inside the specimen, it propagated in a circular or elliptical shape and the specimen showed high fatigue strength, enough to reach the fatigue limit within tolerance of design stresses.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.76-78
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• 2002

Heat shock proteins (HSPs) are induced in most living cells by mild heat treatment, ethanol, heavy metal ions and hypoxia. In yeast Saccharomyces cerevisiae, mild heat pretreatment strongly induces Hsp104 and thus provide acquired thermotolerance. The ability of hsp104 deleted mutant $({\triangle}hsp104)$ to acquire tolerance to extreme temperature is severely impaired. In providing thermotolerance, two ATP binding domains are indispensible, as demonstrated in ClpA and ClpB proteases of E. coli. The mechanisms by which Hsp104 protects cells from severe heat stress are not yet completely elucidated. We have investigated regulation of mitochondrial metabolic pathways controlled by the functional Hsp104 protein using $^{13}C_NMR$ spectroscopy and observed that the turnover rate of TCA cycle was enhanced in the absence of Hsp104. Production of ROS, which are toxic to kill cells radiply via oxidative stress, was also examined by fluorescence assay. Mitochondrial dysfunction was manifested in increased ROS levels and higher sensitivity for oxidative stress in the absence of Hsp104 protein expressed. Finally, we have identified mitochondrial complex I and Ferritin as binding protein(s) of Hsp104 by yeast two hybrid experiment. Based on these observations, we suggest that Hsp104 protein functions as a protector of oxidative stress via either keeping mitochondrial integrity, direct binding to mitochonrial components or regulating metal-catalyzed redox chemistry.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.6
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• pp.396-406
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• 2004

Current physical and chemical methodologies, conventionally used to clean up metal contaminated soils, are generally too expensive to apply in large hazardous waste sites including agricultural lands adjacent to closed or abandoned metal mines. Phytoremediation using plants to extract, sequester and detoxify environmental pollutants is one of the cost-effective and aesthetically-pleasing alternatives, compared with environmentally destructive remedial methods currently being practiced. But, phytoremediation has some limitations such as time consuming and low performance: in general, it is seasonally dependent and slower in removing metals than other methods, and metal accumulating plants are slow growers. Improvement of plants for metal tolerance, accumulation, and translocation using genetic engineering techniques recently opened up new possibilities for phytoremediation. In this paper, we have discussed about recent developments in conventional and genetically engineered phytoremediation. For the conventional phytoremediation, focuses are on the natural hyperaccumulator and the chemically assisted phytoremediation. Some pros and cons on the phytoremediation using transgenic plants, coupled with focusing on the mechanistic view points, are also discussed. It might be concluded that the transgenic plants will be effective tools in the practical application of phytoremediation especially for the highly contaminated soils but mechanisms involved should be deeply understood in advance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.6
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• pp.3114-3119
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• 2013

The mangrove ecosystems have the capacity to act as a sink of heavy metals entering aquatic ecosystems. Despite their potential exposure to metal contaminated sediments, mangroves appear to be highly tolerant to heavy metals. In this study, we cloned metal tolerance gene from mangrove plant. Using CTAB method, RNA were isolated from leaves and root tissue of Rhizophora stylosa habitated at Weno island in Micronesia Chuuk lagoon using CTAB method and phytochelatin synthase 1 (PCS1) gene was cloned using gene specific primers. Expression of PCS1 gene was increased 1.91 fold and 2.72 fold in mangrove propagules exposed to 100 ppb Cd and 10 ppb Cu, respectively. These results indicate that expression of PCS1 gene are promising tools for health assessment of mangrove ecosystem.