• Journal of Ecology and Environment
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• 제31권2호
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• pp.131-137
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• 2008

This study investigated the population densities and diversity of heterotrophic bacteria, and the rhizosphere-to-soil ratios (R/S) in the rhizosphere soil of halophyte Phragmites communis at the western coastal mudflats of Korea. The population densities of aerobic heterotrophic bacteria on the rhizosphere soil of P. communis were in the range of $3.3\;{\pm}\;0.9\;{\times}\;10^7\;{\sim}\;1.2\;{\pm}\;0.5\;{\times}\;10^8\;cfu\;g^{-1}$ dry weight (d. wt.). Population densities of amylolytic bacteria ranged from $1.1\;{\pm}\;0.2\;{\times}\;10^6$ to $3.0\;{\pm}\;1.2\;{\times}\;10^6\;cfu\;g^{-1}\;d.\;wt.$, while those of cellulolytic bacteria and proteolytic bacteria ranged from $5.6\;{\pm}\;2.3\;{\times}\;10^6$ to $1.5\;{\pm}\;0.3\;{\times}\;10^7\;cfu\;g^{-1}\;d.\;wt.$ and from $1.4\;{\pm}\;0.3\;{\times}\;10^6$ to $3.5\;{\pm}\;2.3\;{\times}\;10^7 \;cfu\;g^{-1}\;d.\;wt.$, respectively. The R/S ratios ranged from 2.26 to 6.89. Genetic (16S DNA) analysis of fifty-one isolates from the roots of P. communis suggested that the dominant species were closely related to the ${\gamma}$-proteobacteria group (18 clones) and the ${\alpha}$-proteobacteria group (14 clones). We found that halophyte species and mudflat environment both affected the rhizosphere bacterial communities.

• Journal of Periodontal and Implant Science
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• 제38권4호
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• pp.639-644
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• 2008

Purpose: The aim of this study was to compare the number of live and dead bacteria attached to, or within, the stratified squamous epithelium lining the tissue side of the gingival sulcus. Materials and Methods: A total of 50 patients was examined and classified into healthy or diseased sites according to inflammatory status of the gingival tissue. The surface of stratified squamous epithelium was removed by gentle scraping of the gingival sulcus with curettes. The cells were processed in the laboratory by density-gradient centrifugation to separate the epithelial cells from the loose bacteria and debris. The LIVE/$DEAD^{(R)}$ $BacLight^{TM}$ Bacterial Viability Kit was applied and the specimens were observed by an epifluorescent microscope and the number of bacteria was counted. Results: Live and dead bacteria were stained to green and red, irrespectively. Generally, the number of total bacteria in the diseased sites was significantly higher than in the healthy sites. The mean number of detected bacteria in the diseased sites was $58.6{\pm}36.0$ (red bacteria $10.4{\pm}9.2$ / green bacteria $48.2{\pm}30.5$), while it was $1.5{\pm}1.7$ in the healthy sites (red bacteria $0.1{\pm}0.3$ / green bacteria $1.4{\pm}1.5$). The percentage of red bacteria was $17.5{\pm}11.2%$ in the diseased sites and $2.0{\pm}5.8%$ in the healthy sites. Conclusion: The total number of bacteria in the diseased sites was significantly higher than that of the healthy sites. The ratio and the number of red bacteria were also significantly higher in the diseased sites.

• 생명과학회지
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• 제14권6호
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• pp.891-894
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• 2004

배급수관망에 사용되는 아연도강관과 탄소강관이, 수돗물속에서 생장시키는 생물막의 세균농도와 미생물군집의 양상을 비교하기 위하여 Biolog GN plate를 이용한 CLPP를 수행하였다. 세균농도는 $10^4\;-\;10^6\;CFU/cm^2$이었고, 탄소강관과 아연도강관에 따른 생물막의 세균농도는 유의한 차이가 없었다. 평균적인 발색양상은 비슷하였지만 개별적인 CLPP 양상은 재질과 시기에 따라 다른 것으로 나타나, 미생물군집의 양상이 시간과 재질에 따라 다른 것을 알 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제24권12호
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• pp.1707-1718
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• 2014

In this study, the phylogenetic diversities of bacterial and archaeal communities in a plant-microbial fuel cell (P-MFC) were investigated together with the environmental parameters, affecting its performance by using rice as a model plant. The beneficial effect of the plant appeared only during a certain period of the rice-growing season, at which point the maximum power density was approximately 3-fold higher with rice plants. The temperature, electrical conductivity (EC), and pH in the cathodic and anodic compartments changed considerably during the rice-growing season, and a higher temperature, reduced difference in pH between the cathodic and anodic compartments, and higher EC were advantageous to the performance of the P-MFC. A 16S rRNA pyrosequencing analysis showed that the 16S rRNAs of Deltaproteobacteria and those of Gammaproteobacteria were enriched on the anodes and the cathodes, respectively, when the electrical circuit was connected. At the species level, the operational taxonomic units (OTUs) related to Rhizobiales, Geobacter, Myxococcus, Deferrisoma, and Desulfobulbus were enriched on the anodes, while an OTU related to Acidiferrobacter thiooxydans occupied the highest proportion on the cathodes and occurred only when the circuit was connected. Furthermore, the connection of the electrical circuit decreased the abundance of 16S rRNAs of acetotrophic methanogens and increased that of hydrogenotrophic methanogens. The control of these physicochemical and microbiological factors is expected to be able to improve the performance of P-MFCs.

• Journal of Forest and Environmental Science
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• 제30권2호
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• pp.179-188
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• 2014

This research reports the effects of shifting cultivation on soil environment collecting samples from 0-5 cm soil depth from five locations viz. at Burburichhara, Maichchari, Longadu, Sukurchhari and Muralipara in Rangamati district of Chittagong Hill Tracts (CHTs). Soil analyses showed that fungal and bacterial population, microbial respiration and active microbial biomass, maximum water holding capacity, conductivity and moisture contents were significantly (at least $p{\leq}0.05$) lower in shifting cultivated soil compared to adjacent mixed tree plantations at all the sites. On an average in soils of 5 different shifting cultivated lands fungal population was $1.33{\times}10^5$ CFU/g dry soil and bacterial population $1.80{\times}10^7$ CFU/g dry soil and in mixed plantations fungal population was $1.70{\times}10^5$ and bacterial population $2.51{\times}10^7$ CFU/g dry soil. Organic matter and exchangeable Ca and Mg contents were significantly (at least $p{\leq}0.05$) lower and bulk density significantly (at least $p{\leq}0.05$) higher in shifting cultivated land in most of the locations compared to adjacent mixed tree plantations. Ratios of microbial respiration and organic carbon as well as active microbial biomass and organic carbon were distinctly lower and pH higher at 3 locations in shifting cultivated soils compared to mixed plantations. Findings of various soil properties, therefore, suggest that shifting cultivation has deteriorating effects on soil environment.

• The Plant Pathology Journal
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• 제15권3호
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• pp.162-167
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• 1999

Integration of microbial antagonists with fungicides was tried to control the gray mold caused by Botrytis cinerea on pepper in greenhouse conditions and to reduce fungicide uses. All of the selected bacterial antagonists, Bacillus amyloliquefaciens BL3, Paenibacillus polymyxa BL4, and Pseudomonas putida Cha94, completely inhibited the conidial germination of B. cinerea until 30 days after treatment. However, bacterial colonization of pepper phylloplane was poor in BL4, while the other bacterial isolates and the fungal antagonist Trichoderma harzianum TM colonized well on the phylloplane, maintaining the population density of 104-105 cfu/g until 15 days after microbial treatments. Out of 13 kinds of selected fungicides used for gray mold diseases, polyoxin B and BKF 1995 showed the most discriminatory activity on the fungal growth between B. cinerea and TM. TM grew readily on the media containing those fungicides, while B. cinerea showed poor or no mycelial growth on them. The selected fungicides and antagonists alone reduced incidence of gray mold on pepper, showing disease indices of about 2.4 to 3.0, while its was increased up to 4.2 in the untreated control. Alternate treatments with the antagonists and 2-fold diluted fungicides inhibited the disease incidence as much as the antagonists or fungicides alone, and reduced the secondary inoculum more than the single treatments. This suggests that integration of antagonists and fungicides may be an efficient way to reduce fungicide sprays with reliable control efficacy of the disease. However, there was not much difference in the early and mid-term disease progress among the treatments and the untreated control, probably due to extremely favorable environmental conditions for the disease development in this experiment.

• The Korean Journal of Ecology
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• 제23권5호
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• pp.369-375
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• 2000

도시에서 토양을 보존하고 합리적으로 이용하기 위하여 도시 토양을 과학적으로 이해하는 것이 필요하지만 아직까지 이처럼 과도하게 관리되고 교란된 토양의 특성에 대하여 집중적으로 연구되지 않았다. 본 연구에서 조사된 인천의 산림, 잔디밭, 가로수, 나지 및 포장 밑 토양에서 답압에 의한 견밀화에 의하여 토양 가밀도가 높았다. 또한 다양한 도시 토양에서 수분함량은 전원지 산림 토양에 비하여 적었고 지온은 높았다. 화학적으로는 도시 토양에서 pH가 중성에 가깝고 유기물 함량이 적었다. 도시 토양의 총세균수는 전원지 산림 토양의 단지 5∼50% 수준이었다. 단계식 다중회귀분석의 결과, 토양 유기물함량이 총세균수에 영향을 미치는 주요한 요인으로서 선정되었다. 대부분의 도시 토양에서 탈수소효소 활성도는 전원지 산림 토양과 유의한 차이가 없었으나, 아스팔트 포장 밑 토양에서는 낮았다 그러므로 견밀한 도시 토양에서 낮은 유기물함량이 물질 순환에 관여하는 미생물 수에 악영향을 미친다고 판단되었다.

• 미생물학회지
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• 제50권1호
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• pp.84-86
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• 2014

길항균을 생물 농약으로 개발하기 위해서는 저렴한 산업용 배지를 이용한 대량 생산 체계를 확립하는 것이 중요하다. 본 연구에서는 풋마름병 방제 효과가 뛰어난 Bacillus amyloliquefaciens SKU-78 균주의 배양조건을 확립하였다. 저가의 산업용 기질로는 콩가루와 옥수수 전분 배지가 균 생장에 가장 효과적이었고, 최초 pH 5.5, 배양 온도 $30^{\circ}C$, 교반속도 150-250 rpm의 조건으로 30 L fermenter를 이용한 배양에서 20 시간째에 최대 생균수($1.2{\times}10^{11}$ CFU/ml)에 도달하였다. 저가의 산업용 배지로 배양한 배양액을 관주 처리하였을 때 65%의 발병 억제 효과를 나타냄으로써 SKU-78 균주의 산업용 배지를 이용한 대량배양의 기초가 마련되었다.

• 한국축산식품학회지
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• 제37권4호
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• pp.502-510
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• 2017

This study investigated bacterial growth-inhibitory effect of 69 therapeutic herbal plants extracts on 9 bacterial strains using a disc diffusion assay. Especially, the antimicrobial activity of Psoraleae semen, which showed different activity on pathogenic Gram-positive and Gram-negative bacteria, was evaluated by MIC (minimal inhibition concentration) and biofilm formation assay. The effect of Psoraleae semen extract on bacterial cell membranes was examined by measurement of protein leakage (optical density at 280 nm) and scanning electron microscope (SEM). No clear zone was formed on discs containing Gram-negative bacteria, but Gram-positive bacteria exhibited clear zones. The MICs of Psoraleae semen extract were $8{\mu}g/mL$ for Streptococcus mutans, and $16{\mu}g/mL$ for Enterococci and Staphylococcus aureus. In addition, biofilm formation was inhibited at concentration $8-16{\mu}g/mL$. Protein leakage values and SEM images revealed that cell membranes of Gram-positive bacteria were impaired following exposure to the extract. Further, the extract inhibited the growth of Listeria monocytogenes in sausages. These results indicate that Psoraleae semen extract could be utilized as a natural antimicrobial agent against Gram-positive bacteria.

• The Plant Pathology Journal
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• 제20권2호
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• pp.97-102
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• 2004

Paenibacillus polymyxa E681, with its plant growth promotion and root colonization ability, has been proven to be a promising biocontrol agent of cucumber and barley. This study investigated the attributes related to the movement of bacteria from the seed to the radicle and to the whole root system. It also illustrated the existing form and population changes of the bacteria on seed and root using the scanning electron microscope and confocal laser scanning microscopy. The bacteria invaded and colonized the inside of the seed coat while the seeds were soaked in bacterial suspension. Almost the same number of bacteria on seed surface invaded the inside of the seed coat right after seed soaking. The population densities of E681 increased greatly inside as well as on the surface of the seed before the radicle emerged. The bacteria attached on the emerging radicle directly affected the initial population of newly emerg-ing root. The colonized cells on the root were arranged linearly toward the elongation of the root axis. In addition to colonizing the root surface, strain E681 was found inside the roots, where cells colonized the inter-cellular space between certain epidermal and cortical cells. When the cucumber seeds were soaked in bacterial suspension and sown in pot, the bacterial populations attached on both the surface and inside of the root were sustained up to harvesting time. This means that E681 successfully colonized the root of cucumber and sustained its population density up to harvesting time through seed treatment.