• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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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.

• The Plant Pathology Journal
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• v.20 no.2
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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.

• Journal of Microbiology and Biotechnology
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• v.30 no.11
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• pp.1640-1650
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• 2020

Colorectal cancer (CRC) is the leading cause of common malignant neoplasm worldwide. Many studies have analyzed compositions of gut microbiota associated with various diseases such as inflammatory bowel diseases (IBD) and colon cancer. One of the most representative bacteria involved in CRC is enterotoxigenic Bacteroides fragilis (ETBF), a species belonging to phylum Bacteroidetes. We used ETBF colonized mice with azoxymethane (AOM)/dextran sulphate sodium (DSS) and zerumbone, a compound with anti-bacterial effect, to determine whether zerumbone could restore intestinal microbiota composition. Four experimental groups of mice were used: sham, ETBF colonized AOM/DSS group, ETBF colonized AOM/DSS group zerumbone 60 mg kg-1 (ETBF/AOM/DSS + Z (60)), and only zerumbone (60 mg kg^-1)-treated group. We performed reversible dye terminators-based analysis of 16S rRNA gene region V3-V4 for group comparison. Microbiota compositions of ETBF/AOM/DSS + Z (60) group and ETBF colonized AOM/DSS group not given zerumbone were significantly different. There were more Bacteroides in ETBF/AOM/DSS + Z (60) group than those in ETBF colonized AOM/DSS group, suggesting that B. fragilis could be a normal flora activated by zerumbone. In addition, based on linear discriminant analysis of effect size (LEfSe) analysis, microbial diversity decreased significantly in the ETBF colonized AOM/DSS group. However, after given zerumbone, the taxonomic relative abundance was increased. These findings suggest that zerumbone not only influenced the microbial diversity and richness, but also could be helpful for enhancing the balance of gut microbial composition. In this work, we demonstrate that zerumbone could restore the composition of intestinal microbiota.

• Journal of Microbiology and Biotechnology
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• v.24 no.2
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• pp.280-286
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• 2014

Four thermophilic bacterial species, including the iron-reducing bacterium Geobacillus sp. G2 and the sulfate-reducing bacterium Desulfotomaculum sp. SRB-M, were employed to integrate a bacterial consortium. A second consortium was integrated with the same bacteria, except for Geobacillus sp. G2. Carbon steel coupons were subjected to batch cultures of both consortia. The corrosion induced by the complete consortium was 10 times higher than that induced by the second consortium, and the ferrous ion concentration was consistently higher in iron-reducing consortia. Scanning electronic microscopy analysis of the carbon steel surface showed mineral films colonized by bacteria. The complete consortium caused profuse fracturing of the mineral film, whereas the non-iron-reducing consortium did not generate fractures. These data show that the iron-reducing activity of Geobacillus sp. G2 promotes fracturing of mineral films, thereby increasing steel corrosion.

• Korean Journal Plant Pathology
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• v.14 no.6
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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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• v.43 no.4
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• pp.345-353
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• 2005

The complex ecosystem of intestinal micro flora is estimated to harbor approximately 400 different microbial species, mostly bacteria. However, studies on bacterial colonization have mostly been based on culturing methods, which only detect a small fraction of the whole microbiotic ecosystem of the gut. To clarify the initial acquisition and subsequent colonization of bacteria in an infant within the few days after birth, phylogenetic analysis was performed using 16S rDNA sequences from the DNA iso-lated from feces on the 1st, 3rd, and 6th day. 16S rDNA libraries were constructed with the amplicons of PCR conditions at 30 cycles and $50^{\circ}C$ annealing temperature. Nine independent libraries were produced by the application of three sets of primers (set A, set B, and set C) combined with three fecal samples for day 1, day 3, and day 6 of life. Approximately 220 clones ($76.7\%$) of all 325 isolated clones were characterized as known species, while other 105 clones ($32.3\%$) were characterized as unknown species. The library clone with set A universal primers amplifying 350 bp displayed increased diversity by days. Thus, set A primers were better suited for this type of molecular ecological analysis. On the first day of the life of the infant, Enterobacter, Lactococcus lactis, Leuconostoc citreum, and Streptococcus mitis were present. The largest taxonomic group was L. lactis. On the third day of the life of the infant, Enterobacter, Enterococcus faecalis, Escherichia coli, S. mitis, and Streptococcus salivarius were present. On the sixth day of the life of the infant, Citrobacter, Clostridium difficile, Enterobacter sp., Enterobacter cloacae, and E. coli were present. The largest taxonomic group was E. coli. These results showed that microbiotic diversity changes very rapidly in the few days after birth, and the acquisition of unculturable bacteria expanded rapidly after the third day.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.1
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• pp.35-43
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• 2017

This study was to research the relationships between rice straw degradation and changes of fibrolytic bacteria population during the in vitro rumen fermentation. Dry matter(DM) digestion of rice straw and population of fibrolytic bacteria were measured at the 0. 4, 8, 12 and 48 hours during the incubation. The populations of F. succinogenes. R. albus and R. flavefaciens were defined as log copy number of 16S rDNA by technical method of Quantitative real-time PCR. Total population of F. succinogenes, R. flavefaciens and R. albus was sum of bactera attached on rice straw and suspended in medium. It's population was increased with incubation, reached top level of 29.0 Log copy No at the 24 hour and then decreased. In the meantime, DM digestion of rice straw showed the higher increasement from the 8 hour to the 24 hour than from the 0 hour to the 8 hour, and then a slowdown in increasing trend of digestibility. Attachments of F. succinogenes, R. flavefaciens and R. albus were detected immediately after start of in vitro rumen incubation. At the same time, the colonized bacterial share were respectively 34.5%, 84.4% and 67.9% in total population. All of them was reached the highest colonized bacterial share above 94.7% at the 4 hour incubation. However population of attached bacteria was shown the highest level at the 12 hour or the 24 hour incubation. Kinetics of colonization were formed area of top speed from the 12 hour to the 24 hour and respectively reached 10.33, 9.28 및 8.30 Log copy No/h/g DM at the 24 hour by F. succinogenes, R. flavefaciens and R. albus. The kinetics of rice straw degradation was formed top level of 0.95% DM/h at the 24 hour. The present results gave clear evidence that degradation of rice straw was increased with the development of total fibrolytic bacteria in process of rumen fermentation. Also, their attachment was largely occurred immediately after insertion of rice straw, the colonized bacteria was actively proliferated, and then degradation of rice straw was maximized.

• Journal of Soil and Groundwater Environment
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• v.21 no.4
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• pp.50-59
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• 2016

Spatial and temporal changes in nitrification activities and distribution of microbial population of ammonia oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) in paddy soils were investigated. Soil samples were collected in March and October 2015 from rice paddy with and without the presence of confined animal feeding operations. Incubation experiments and quantitative polymerase chain reaction showed that AOA's contribution to nitrification kinetics was much higher in locations where organic nitrogen in animal waste is expected to significantly contribute to overall nitrogen budget, and temporal variations in nitrification kinetics were much smaller for AOA than AOB. These differences were interpreted to indicate that different microbial responses of two microbial populations to the types and concentrations of nitrogen substrates were the main determining factors of nitrification processes in the paddy soils. The copy numbers of ammonium monooxygenase gene showed that AOA colonized the paddy soils in higher numbers than AOB with stable distribution while AOB showed variation especially in March. Although small in numbers, AOB population turned out to exert more influence on nitrification potential than AOA, which was attributed to higher fluctuation in AOB cell numbers and nitrification reaction rate per cells.

• The Plant Pathology Journal
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• v.34 no.5
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• pp.403-411
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• 2018

This study takes strawberry-fruits as the test material and discusses the effect of Burkholderia contaminans B-1 on preventing postharvest diseases and inducing resistance-related substances in strawberry-fruits. Soaking and wound inoculating is performed to analyze the inhibitory effects of different treatment solutions on the gray mold of postharvest strawberry-fruits. The count of antagonistic bacteria colonies in the wound is found, and the dynamic growth of antagonistic bacteria and the pathogenic fungus is observed by electron microscopy. The results indicated that, either by soaking/wound-inoculating, the fermentation and suspension of antagonistic bacteria significantly reduced the incidence of postharvest diseases of strawberry-fruits. With wound inoculation, the inhibition rate of antagonist fermentation and suspension ($1{\times}10^{10}cfu/ml$) respectively reached 77.4% and 66.7%. It also led to a significant increase in the activity of resistance-related enzymes, i.e., phenylalanine ammonia lyase (PAL), 4-coumarate coenzyme A ligase (4CL), cinnamate-4-hydroxylase (C4H) and chalcone isomerase (CHI). On 1 d and 2 d post-treatment, the activity of 4CL was respectively 3.78 and 6.1 times of the control, and on 5 d, the activity of PAL was increased by 4.47 times the control. The treatment of antagonistic bacteria delayed the peaking of cinnamyl-alcohol dehydrogenase (CAD) activity and promoted the accumulation of lignin and total phenols. The antagonistic bacteria could be well colonized in the wounds. On 4-5 d post-inoculation, the count of colonies was $10^8$ times of that upon inoculation. Electronmicroscopy indicated that the antagonistic bacteria delayed the germination of pathogenic spores in the wounds, and inhibited further elongations of the mycelia.

• Microbiology and Biotechnology Letters
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• v.48 no.3
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• pp.276-286
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• 2020

Probiotics are live microorganisms that, when administered in adequate amounts, confer health benefits to the host. This study was conducted for the isolation of potential lactic acid bacteria (LAB) with probiotic properties from goat milk and yogurt. Several tests were conducted in vitro using the standard procedures for evaluating the inhibitory spectra of LAB against pathogenic bacteria; tolerance to NaCl, bile salt, and phenol; hemolytic, milk coagulation, and bile salt hydrolase activities; gastrointestinal transit tolerance; adhesion properties; and antibiotic susceptibility. Among 40 LAB strains screened according to culture characteristics, five isolates exhibited antagonistic properties. Three were identified as Pediococcus acidilactici, and two were identified as Enterococcus faecium, exploiting 16S rRNA gene sequencing. All the isolates succeeded in the gastrointestinal transit tolerance assay and successively colonized mucosal epithelial cells. Based on the results of these in vitro assays, both P. acidilactici and E. faecium can be considered as potential probiotic candidates.