• The Plant Pathology Journal
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• 제32권2호
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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.

• 한국식물병리학회지
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• 제14권6호
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• pp.598-602
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• 1998

Twenty two rhizobacteria were isolated from the roots and rhizosphere of radish, carnation, potato and tomato. There isolates produced a fluorescent pigment in King's B medium and identified as Pseudomonas spp. These isolates colonized roots and rhizosphere of the host plants. In the study of cultural characteristics of the bacteria, the pH of the culture broth was changed from neutral (7.0) to alkali (8.8∼9.41) and the numbers of cells were increased from 106 to 108 after 40 hr of incubation in basal standard succinate medium. The salicylic acid production identified by pink color reaction were observed in 7 bacteria. Out of these 7 salicylic acid producing bacteria, only 2 strains of bacteria such as Pseudomonas fluorescens RS006, and Pseudomonas sp. EN401 were confirmed as salicylic acid producers by optical density measurement. Therefore, for screening of salicylic acid producing bacteria from the roots and rhizosphere, color reaction of the culture medium should be done in the first step, and then optical density measurement of culture extract should be made for the confirmation of salicylic acid production.

• Journal of Microbiology
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• 제43권6호
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• pp.572-576
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• 2005

This study focused on detecting catabolic genes for polycyclic aromatic hydrocarbons (PAHs) distributed in the reed rhizosphere of Sunchon Bay, Korea. These marsh and mud environments were severely affected by human activities, including agriculture and fisheries. Our previous study on microbial roles in natural decontamination displayed the possibility that PAH-degrading bacteria, such as Achromobacter sp., Alcaligenes sp., Burkholderia sp. and Pseudomonas sp. play an important decontamination role in a reed rhizosphere. In order to gain further fundamental knowledge on the natural decontamination process, catabolic genes for PAH metabolism were investigated through PCR amplification of dioxygenase genes using soil genomic DNA and sequencing. Comparative analysis of predicted amino acid sequences from 50 randomly selected dioxygenase clones capable of hydroxylating inactivated aromatic nuclei indicated that these were divided into three groups, two of which might be originated from PAH-degrading bacteria. Amino acid sequences of each dioxygenase clone were a part of the genes encoding enzymes for initial catabolism of naphthalene, phenanthrene, or pyrene that might be originated from bacteria in the reed rhizosphere of Sunchon Bay.

• Journal of Microbiology and Biotechnology
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• 제32권10호
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• pp.1292-1298
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• 2022

Soil autotrophic bacterial communities play a significant role in the soil carbon (C) cycle in paddy fields, but little is known about how rhizosphere soil microorganisms respond to different long-term (35 years) fertilization practices under double rice cropping ecosystems in southern China. Here, we investigated the variation characteristics of rhizosphere soil RubisCO gene cbbL in the double rice ecosystems of in southern China where such fertilization practices are used. For this experiment we set up the following fertilizer regime: without any fertilizer input as a control (CK), inorganic fertilizer (MF), straw returning (RF), and organic and inorganic fertilizer (OM). We found that abundances of cbbL, 16S rRNA genes and RubisCO activity in rhizosphere soil with OM, RF and MF treatments were significantly higher than that of CK treatment. The abundances of cbbL and 16S rRNA genes in rhizosphere soil with OM treatment were 5.46 and 3.64 times higher than that of CK treatment, respectively. Rhizosphere soil RubisCO activity with OM and RF treatments increased by 50.56 and 45.22%, compared to CK treatment. Shannon and Chao1 indices for rhizosphere soil cbbL libraries with RF and OM treatments increased by 44.28, 28.56, 29.60, and 23.13% compared to CK treatment. Rhizosphere soil cbbL sequences with MF, RF and OM treatments mainly belonged to Variovorax paradoxus, uncultured proteobacterium, Ralstonia pickettii, Thermononospora curvata, and Azoarcus sp.KH33C. Meanwhile, cbbL-carrying bacterial composition was obviously influenced by soil bulk density, rhizosphere soil dissolved organic C, soil organic C, and microbial biomass C contents. Fertilizer practices were the principal factor influencing rhizosphere soil cbbL-carrying bacterial communities. These results showed that rhizosphere soil autotrophic bacterial communities were significantly changed under conditions of different long-term fertilization practices Therefore, increasing rhizosphere soil autotrophic bacteria community with crop residue and organic manure practices was found to be beneficial for management of double rice ecosystems in southern China.

• 미생물학회지
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• 제46권3호
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• pp.278-285
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• 2010

국내에 자생하는 당귀, 삽주, 쇠무릎, 지모, 황기의 근권토양내 EPS 생성균주의 분포율을 조사한 결과 당귀로부터 분리된 균주의 56%가 EPS 생성 균주로 가장 높은 분포율을 나타내었다. 또한, 당귀 근계 (근권, 근면, 근 내부) 내 EPS 생성 세균의 밀도를 측정한 결과, 근권 토양 내에는 $9.0{\times}10^6$ CFU/$g{\cdot}soil$, 근면에는 $7.0{\times}10^6$ CFU/$g{\cdot}soil$, 그리고, 근 내부에는 $1.4{\times}10^3$ CFU/$g{\cdot}soil$로 확인되어, 다수의 EPS 생성 세균이 분포하고 있음이 확인되었다. 당귀 근권으로부터 분리된 EPS 생성세균은 Alphaproteobacteria (4 strains), Betaproteobacteria (6 strains), Firmicutes (2 strains), Actinobacteria (3 strains), 그리고 Bacteroidetes (1 strain) 계통군에 속하는 균주였다. 근면으로 부터 분리된 EPS 생성세균은 Alphaproteobacteria (7 strains), Betaproteobacteria (3 strains), Actinobacteria (2 strains), Bacteroidetes (3 strains), 그리고 Acidobacteria (1 strain) 계통군으로 나타났으며, 근 내부에서 분리된 EPS 생성세균은 모두 Bacteroidetes 계통군 Chitinophaga에 속하는 특징을 나타내었다. 약초 근권토양으로부터 분리된 EPS 생성세균 112균주중에서 Burkholderia caribiensis DR14 (1,547 mpa.s), Terriglobus sp. DRP35균주(2,136 mpa.s), Rhizobium hainanense SAP110균주(1,680 mpa.s)를 최우수 EPS 생성 균주로 선발하였다. 분리 정제된 EPS를 Bio-LC로 분석한 결과 glucose, galactose, mannose의 중성당과, galactosamine, glucosamine의 아미노당이 나타났다. 특히 Rhizobium hainanense SAP110 균주는 주요 중성당으로 glucose (60-89%)를 그리고 주요 아미노당으로 glucosamine (8.5%)을 생성하는 특징을 나타내었다.

• 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 Ecology and Environment
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• 제29권4호
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• pp.399-404
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• 2006

This study was carried out to investigate the population densities, R/S ratios, and identification of heterotrophic bacteria on the rhizosphere soil of halophyte Suaeda japonica found on the western and southern mudflats of Korea. The population densities of aerobic and anaerobic heterotrophic bacteria on the rhizosphere soil of Suaeda japonica were in the range of $1.3\;{\pm}\;0.3\;{\times}\;10^6\;{\sim}\;6.3\;{\pm}\;3.3\;{\times}\;10^7\;and\;2.8\;{\pm}\;1.3\;{\times}\;10^4\;{\sim}\;1.8\;{\pm}\;0.7\;{\times}\;10^7\;cfu\;g^{-1}\;d.\;wt.$, respectively. In case of physiologically specific bacteria, population densities of amylolytic bacteria on the rhizosphere soil of Suaeda japonica were in the range of $4.4\;{\pm}\;0.6\;{\times}\;10^6\;{\sim}\;2.5\;{\pm}\;1.2\;{\times}\;10^7\;cfu\;g^{-1}\;d.\;wt.$, those of cellulolytic bacteria were from $8.5\;{\pm}\;6.0\;{\times}\;10^4\;{\sim}\;2.3\;{\pm}\;1.6\;{\times}\;10^6\;cfu\;g^{-1}\;d.\;wt.$, and those of proteolytic bacteria were from $3.8\;{\pm}\;1.8\;{\times}\;10^5\;{\sim}\;4.2\;{\pm}\;2.9\;{\times}\;10^6\;cfu\;g^{-1}\;d.\;wt.$, respectively. The R/S ratios were ranged from 2.33 to 2.39. Among eleven isolates from the roots of halophyte Suaeda japonica of Goheung bay by using 16S rDNA analysis, five clones were closely related to ${\gamma}-Proteobacteria$ group and six clones were closely related to ${\alpha}-Proteobacteria$ group. Among four isolates from Suncheon bay, two strains were related to ${\gamma}-Proteobacteria$ group and another two were related to Actinobacteria and Bacilli group, respectively.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.93.2-94
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• 2003

In our previous studies, we selected three antagonistic bacteria, KJ1R5, KJ2C12, and KJ9C8 against Phytophthora capsici, the casual agent of Phytophthora blight of pepper. For elucidating production, root colonization, and total microbial activity were investigated. The dual culture assay was accomplished to elucidate existence of antibiotics. In this assay, any antagonistic bacteria did not inhibit growth of six important fungal plant pathogens, suggesting that these antagonists do not produce antibiotics. root surface or rhizosphere soil colonizations were examined with spontaneous rifampicin-resistant mutants equal to antagonistic ability of wild types. KJ2C12 colonized consistently rhizosphere soil while yellowish colonies of KJ1R5 and KJ9C8 well colonized root surfaces and rhizosphere soil. Total microbial activity in pots treated with the antagonistic bacteria was measured using fluorescein diacetate hydrolysis. total microbial activity of three antagonistic bacteria treatments was significantly higher than that of buffer-treated control until 4days after treatment. However, total microbial activity of treatment of three antagonistic bacteria decreased after 7 days. These results indicate that the antagonistic bacteria, KJ1R5 and KJ9C8 colonized and protected roots well against Phytophthora blight of pepper through competition of infection courts, especially competitions.

• 한국토양비료학회지
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• 제41권1호
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• pp.9-17
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• 2008

식물에 필수영양소인 황은 대부분 sulfate의 형태로 식물이 흡수하며, thiosulfate 형태로는 영양소로서 흡수하지 못한다. 황산화세균은 이러한 thiosulfate를 산화시켜 sulfate로 만들어 준다. 국내 토양에서 황산화세균의 분포를 조사하기 위하여 경제적으로 중요성을 갖는 19가지 작물의 근권에서 토양을 채취하였다. 항산화세균은 조사한 모든 작물의 근권에서 존재하였으며, 황산화능이 우수한 32가지의 황산화세균을 분리하였다. 또한 분리 균주의 생화학적 특징을 검토한 결과 32종 중 56%가 필수 화학합성자가영양생물이었으며, 44%가 기생 종속영양생물이었다. 분리 균주 ATSR15P는 배양과정에서 19.2 mM의 thiosulfate를 사용하였고, 11.7 mM의 sulfate를 축적하였다. 또한 ATSR15P 배양 과정 중 배지의 pH가 6.5에서 3.1로 감소하였다. 본 연구에서는 황산화세균에 의 한 황의 산화가 국내 작물의 근권에서 포괄적으로 나타나는 현상이라는 것을 증명하고 있다.

• Journal of Microbiology
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• 제43권3호
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• pp.219-227
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• 2005

Little is known about the bacterial communities associated with the plants inhabiting sand dune ecosystems. In this study, the bacterial populations associated with two major sand dune plant species, Calystegia soldanella (beach morning glory) and Elymus mollis (wild rye), growing along the costal areas in Tae-An, Chungnam Province, were analyzed using a culture-dependent approach. A total of 212 bacteria were isolated from the root and rhizosphere samples of the two plants, and subjected to further analysis. Based on the analysis of the 16S rDNA sequences, all the bacterial isolates were classified into six major phyla of the domain Bacteria. Significant differences were observed between the two plant species, and also between the rhizospheric and root endophytic communities. The isolates from the rhizosphere of the two plant species were assigned to 27 different established genera, and the root endophytic bacteria were assigned to 21. Members of the phylum Gammaproteobacteria, notably the Pseudomonas species, comprised the majority of both the rhizospheric and endophytic bacteria, followed by members of Bacteroidetes and Firmicutes in the rhizosphere and Alphaproteobacteria and Bacteroidetes in the root. A number of isolates were recognized as potentially novel bacterial taxa. Fifteen out of 27 bacterial genera were commonly found in the rhizosphere of both plants, which was comparable to 3 out of 21 common genera in the root, implying the host specificity for endophytic populations. This study of the diversity of culturable rhizospheric and endophytic bacteria has provided the basis for further investigation aimed at the selection of microbes for the facilitation of plant growth.