• The Plant Pathology Journal
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• v.32 no.2
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• pp.136-144
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• 2016

Pseudomonas fluorescens pc78 is an effective biocontrol agent for soil-borne fungal diseases. We previously constructed a P43-gfp tagged biocontrol bacteria P. fluorescens pc78-48 to investigate bacterial traits in natural ecosystem and the environmental risk of genetically modified biocontrol bacteria in tomato rhizosphere. Fluctuation of culturable bacteria profile, microbial community structure, and potential horizontal gene transfer was investigated over time after the bacteria treatment to the tomato rhizosphere. Tagged gene transfer to other organisms such as tomato plants and bacteria cultured on various media was examined by polymerase chain reaction, using gene specific primers. Transfer of chromosomally integrated P43-gfp from pc78 to other organisms was not apparent. Population and colony types of culturable bacteria were not significantly affected by the introduction of P. fluorescens pc78 or pc78-48 into tomato rhizosphere. Additionally, terminal restriction fragment length polymorphism profiles were investigated to estimate the influence on the microbial community structure in tomato rhizosphere between non-treated and pc78-48-treated samples. Interestingly, rhizosphere soil treated with strain pc78-48 exhibited a significantly different bacterial community structure compared to that of non-treated rhizosphere soil. Our results suggest that biocontrol bacteria treatment influences microbial community in tomato rhizosphere, while the chromosomally modified biocontrol bacteria may not pose any specific environmental risk in terms of gene transfer.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.181-187
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• 2011

The overall objective of this study is to develop the engineering-friendly-methodology which can investigate the fate of antibiotic resistance in environment microbial community. For this purpose, effective concentration (EC) concept was adopted with cultural based method which is currently used in engineering practice. When a tetracyline antibiotic was present as selective pressure agent among microbial community, activated sludge, the $EC_{50}$ and/or $EC_{90}$ of tetracycline in microbial community were statistically increased compared to control, especially higher growth rate and organic loading conditions of SBRs. Therefore, these results strongly suggested that the continuous monitoring of EC in microbial community can be used for characterizing the fate of tetracycline resistance community in environmental samples.

• Journal of Ecology and Environment
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• v.36 no.4
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• pp.223-233
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• 2013

Acid deposition is one of the most serious environmental problems in ecosystems. The present study surveyed the effects of simulated acid rain on leaf litter mass loss and microbial community in the decomposing leaf litter of Sorbus anifolia in a microcosm at $23^{\circ}C$ and 40% humidity. Microbial biomass was measured by substrate-induced respiration (SIR) and phospholipid fatty acids (PLFAs), and the microbial community structures were determined by composition of PLFAs at each interval of decomposition in litter sample and at each pH treatment. The microbial biomass showed peaks at mid-stage of decomposition, decreasing at the late stage. The leaf litter mass loss of S. anifolia decreased with decreasing pH during early and mid-decomposition stages; however the mass loss becomes similar between pH treatments at late-decomposition stage. The acidification remarkably lowers the microbial biomass of bacteria and fungi; however, microbial diversity was unchanged between pH treatments at each stage of litter decomposition. With changes of decomposition stage and pH treatment there were considerable differences in replacement and compensation of microbial species. Fungi/bacteria ratio was considerably changed by pH treatment. The PLFA profile showed significantly larger fungi/bacteria ratio at pH 5 than pH 3 at the early stage of decomposition, and the difference becomes smaller at the later decomposition stage. At low pH, pH 3 and pH 4, the fungi/bacteria ratios were stable according to the litter decomposition stages. Simulated acid rain caused decreases of 10Me17:0, 16:1${\omega}$7c, 18:1${\omega}$7, 15:0, but increase of 24:0. In addition, litter mass loss showed significant positive correlation with microbial biomass measured by SIR and PLFA on the decomposing leaf litter.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.197-200
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• 2002

• Korean Journal of Microbiology
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• v.46 no.1
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• pp.1-8
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• 2010

New technologies are providing unprecedented knowledge into microbial community structure and functions. Even though nucleic acid based approaches provide a lot of information, metaproteomics could provide a high-resolution representation of genotypic and phenotypic traits of distinct microbial communities. Analyzing the metagenome from different microbial ecosystems, metaproteomics has been applied to seawater, human guts, activated sludge, acid mine drainage biofilm, and soil. Although these studies employed different approaches, they elucidated that metaproteomics could provide a link among microbial community structure, function, physiology, interaction, ecology, and evolution. These approaches are reviewed here to help gain insights into the function of microbial community in ecosystems.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.2
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• pp.194-199
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• 2010

Compost as a soil amendment is of importance in enhancing the soil chemical and microbial qualities; however, soil microbial community can vary depending on the composition, and the amount of compost applied to plant in the soil. Responses of soil microbial properties to compost applications with 0, 30, and 60 Mg $ha^{-1}$ were investigated in silt loam soils where red pepper(Capsicum annuum L.) was mainly cultivated in Yeongyang, Gyeongbuk, Korea. The analysis of phospholipid fatty acids (PLFAs) extracted from soil showed that compost amounts significantly increased PLFAs representing as bacteria, fungi, and VAM-fungi as well as the ratio of fungi/bacteria, and monounsaturated/saturated PLFAs. Increasing the amount of compost significantly increased Gram-/Gram+ PLFAs' ratio, but significantly decreased monounsaturated/saturated PLFAs' ratio. Therefore, this result shows that compost would vary to a limited extent the microbial community in red pepper field. However, increase in compost application would change the subgroup structure of microbial community only.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.2
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• pp.81-86
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• 2015

Soil management for orchard depends on the effects of soil microbial activities. The present study evaluated the soil microbial community of 25 orchard (5 sites for sandy loam, 7 sites for silt loam, and 13 sites for loam) in Gyeongnam Province by fatty acid methyl ester (FAME) method. The average values for 25 orchard soil samples were $270nmol\;g^{-1}$ of total FAMEs, $72nmol\;g^{-1}$ of total bacteria, $34nmol\;g^{-1}$ of Gram-negative bacteria, $34nmol\;g^{-1}$ of Gram-positive bacteria, $6nmol\;g^{-1}$ of actinomycetes, $49nmol\;g^{-1}$ of fungi, and $7nmol\;g^{-1}$ of arbuscular mycorrhizal fungi. In addition, silt loam soils had significantly low ratio of cy17:0 to $16:1{\omega}7c$ and cy19:0 to $18:1{\omega}7c$ compared with those of loam soils (p < 0.05), indicating that microbial activity increased. The average soil microbial communities in the orchard soils were 26.7% of bacteria, 17.9% of fungi, 12.6% of Gram-negative bacteria, 12.5% of Gram-positive bacteria, 2.5% of arbuscular mycorrhizal fungi, and 2.2% of actinomycetes. The soil microbial community of Gram-negative bacteria in silt loam soils was significantly higher than those of sandy loam and loam soils (p < 0.05).

• Journal of Environmental Science International
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• v.10 no.3
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• pp.239-245
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• 2001

This research was performed to investigate the dynamics of microbial community by RBC (Rotating Biological Contactor) using Rhodococcus sp. EL-GT and activated sludge. Cell counts revealed by DAPI were compared with culturable bacterial counts from nutrient agar. Colony counts on nutrient agar gave values 20~25% and 1~15% of cell counts (DAPI). The cell counts for the dynamics of bacterial community were determined by combination of in situ hybridization with fluorescently-labelled oligonyucleotide probes and epifluorescence microscopy. Around 90~80% of total cells visualized DAPI were also detected by the bacteria probe EUB 338. For both reactors proteobacteria belonging to the gamma subclass were dominant in the first stage (1 and 2 stage) and proteobacteria belonging to the gamma subclass were dominant in the last stage (3 and 4 stage).

• The Plant Pathology Journal
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• v.38 no.5
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• pp.425-431
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• 2022

Plant microbiota has influenced plant growth and physiology significantly. Plant and plant-associated microbes have flexible interactions that respond to changes in environmental conditions. These interactions can be adjusted to suit the requirements of the microbial community or the host physiology. In addition, it can be modified to suit microbiota structure or fixed by the host condition. However, no technology is realized yet to control mechanically manipulated plant microbiota structure. Here, we review step-by-step plant-associated microbial partnership from plant growth-promoting rhizobacteria to the microbiota structural modulation. Glutamic acid enriched the population of Streptomyces, a specific taxon in anthosphere microbiota community. Additionally, the population density of the microbes in the rhizosphere was also a positive response to glutamic acid treatment. Although many types of research are conducted on the structural revealing of plant microbiota, these concepts need to be further understood as to how the plant microbiota clusters are controlled or modulated at the community level. This review suggests that the intrinsic level of glutamic acid in planta is associated with the microbiota composition that the external supply of the biostimulant can modulate.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.164-167
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• 2004

To investigate the chemical and microbiological characteristics of groundwater and surface waters in contaminated sites, hydrochemical and microbial community analysis were executed. Different indigenous bacteria were observed at 4 contaminated sites and this is considered to decompose the contaminants of groundwater. The research results showed the close relationship between hydrochemistry and microbial characteristics and those are used for the information of natural attenuation and enhanced bioremediation.