• Journal of Microbiology and Biotechnology
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• v.31 no.9
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• pp.1241-1255
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• 2021

This study was carried out to explore a non-chemical strategy for enhancing productivity by employing some antagonistic rhizobacteria. One hundred eighteen bacterial isolates were obtained from the rhizospheric zone of various crop fields of Gangwon-do, Korea, and screened for antifungal activity against Fusarium wilt (Fusarium oxysporum f. sp. lactucae) in lettuce crop under in vitro and in vivo conditions. In broth-based dual culture assay, fourteen bacterial isolates showed significant inhibition of mycelial growth of F. oxysporium f. sp. lactucae. All of the antagonistic isolates were further characterized for the antagonistic traits under in vitro conditions. The isolates were identified on the basis of biochemical characteristics and confirmed at their species level by 16S rRNA gene sequencing analysis. Arthrobacter sulfonivorans, Bacillus siamensis, Bacillus amyloliquefaciens, Pseudomonas proteolytica, four Paenibacillus peoriae strains, and Bacillus subtilis were identified from the biochemical characterization and 16S rRNA gene sequencing analysis. The isolates EN21 and EN23 showed significant decrease in disease severity on lettuce compared to infected control and other bacterial treatments under greenhouse conditions. Two bacterial isolates, EN4 and EN21, were evaluated to assess their disease reduction and growth promotion in lettuce in field conditions. The consortium of EN4 and EN21 showed significant enhancement of growth on lettuce by suppressing disease caused by F. oxysporum f. sp. lactucae respectively. This study clearly indicates that the promising isolates, EN4 (P. proteolytica) and EN21 (Bacillus siamensis), can be commercialized and used as biofertilizer and/or biopesticide for sustainable crop production.

• Research in Plant Disease
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• v.17 no.1
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• pp.38-43
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• 2011

Almost 10~30% of vegetables were discarded by the spoilage from farms to tables. After harvest, vegetables are often spoiled by a wide variety of microorganisms including many bacterial and fungal species. This investigation was conducted to extent the knowledge of relationship the spoilage of vegetables and the diversity of microbes. The total aerobic bacterial numbers in fresh lettuce, perilla leaf, and chicory were $2.6{\sim}2.7{\times}10^6$, $4.6{\times}10^5$, $1.2{\times}10^6\;CFU/g$ of fresh weight, respectively. The most common bacterial species were Pseudomonas spp., Alysiella spp., and Burkholderia spp., and other 18 more genera were involved in. After one week of incubation of those vegetables at $28^{\circ}C$, the microbial diversity had been changed. The total aerobic bacterial numbers increased to $1.1{\sim}4.6{\times}10^8$, $4.9{\times}10^7$, and $7.6{\times}10^8\;CFU/g$ of fresh weight for lettuce, perilla leaf, and chicory that is about $10^2$ times increased bacterial numbers than that before spoilage. However, the diversity of microbes isolated had been simplified and fewer bacterial species had been isolated. The most bacterial population (~48%) was taken up by Pseudomonas spp., and followed by Arthrobacter spp. and Bacillus spp. The spoilage activity of individual bacterial isolates had been tested using axenic lettuce plants. Among tested isolates, Pseudomonas fluorescence and Pantoea agglomerans caused severe spoilage on lettuce.

• Korean Journal of Microbiology
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• v.39 no.1
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• pp.16-20
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• 2003

A phylogenetic analysis of bacterial populations inhabiting soil derived from serpentine was conducted. The samples were collected from adjacent metamorphic rocks and serpentinite soil at Kwangcheon. The pH of the serpentine areas ranged from 8.5 to 9.2. The number of bacteria on the DAL medium which was diluted with $10^{-2}$ of AL medium was 10~100 fold higher than that from the full strength of AL medium, and which indicates that oligotrophs are distributed in the serpentinite soil. Of a total of 76 isolates, 42 isolates were oligotrophic bacteria, which grew only on the DAL medium. Based on a phylogenetic analysis using 16S rDNA sequences, these isolates are found to fall within five major phylogenetic groups: proteobacteria $\alpha$-subdivision (3 strains), $\alpha$-subdivision (7 strains), $\gamma$-subdivision (2 trains); high G+C gram-positive bacteria (19 strains); low G+C grampositive bacteria (14 strains). Bacteria of the genus Streptomyces (high G+C division) and Bacillus (low G+C division) have been considered to form a numerically important fraction of serpentinite soil. Oligotrophic strains categorized as Afipia ($\alpha$-subdivision), Ralstonia, Variovorax ($\beta$-subdivision), Pseudomonas ($\gamma$ -subdivision), Arthrobacter (high G+C division), and Streptomyces (low G+C division).

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.spc
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• pp.20-28
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• 2009

The sustainability of conventional agriculture which is characterized by input dependent and ecologically simplified food production system is vague. Chemicals and present practices used in agriculture are not only costly but also have widespread implications on human and animal health, food quality and safety and environmental quality. Thus there is a need for alternative farming practices to sustain food production for the escalating population and conserve environment for future generations. The present research scenario in the area of plant microbe interactions for maintaining sustainable agriculture suggests that the level of internal regulation in agro-ecosystems is largely dependent on the level of plant and microbial diversity present in the soil. In agro-ecosystems, biodiversity performs a variety of ecological services beyond the production of food, including recycling of nutrients, regulation of microclimate and local hydrological processes, suppression of undesirable organisms and detoxification of noxious chemicals. Controlling the soil microflora to enhance the predominance of beneficial and effective microorganisms can help improve and maintain soil chemical and physical properties. The role of beneficial soil microorganisms in sustainable productivity has been well construed. Some plant bacteria referred to as plant growth-promoting rhizobacteria (PGPR) can contribute to improve plant growth, nutrient uptake and microbial diversity when inoculated to plants. Term PGPR was initially used to describe strains of naturally occurring non-symbiotic soil bacteria have the ability to colonize plant roots and stimulate plant growth PGPR activity has been reported in strains belonging to several other genera, such as Azotobacter, Azospirillum, Arthrobacter Bacillus, Burkhokderia, Methylobacterium, and Pseudomonas etc. PGPR stimulate plant growth directly either by synthesizing hormones such as indole acetic acid or by promoting nutrition, for example, by phosphate solubilization or more generally by accelerating mineralization processes. They can also stimulate growth indirectly, acting as biocontrol agents by protecting the plant against soil borne fungal pathogens or deleterious bacteria. Present review focuses on some recent developments to evolve strategies for better biotechnological exploitation of PGPR's.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.4
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• pp.476-480
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• 2007

In order to prevent the quality deterioration of rice from microbial infection, we investigated antimicrobial activities of Morun albalinne, Glycyorrhiza uralensis, Sargassum siliquastrum, and Ecklonin cava against isolated microorganisms from the paddy and warehouses. The major types of the bacteria grown in the paddy and rice warehouses were Sphingomonas paucimobilis, Arthrobacter atrocyaneus, and Bacillus spp. such as Bacillus cereus Additionally Deuteromycetes, Aspergillus spp. and Penicillum spp. were considered as major contaminant microorganisms in the paddy and rice warehouses. As results of the paper disc assay against the isolated microorganisms, the ethanol extracts with Morun albalinne, Glycyorrhiza uralensis, Sargassum siliquastrum, and Ecklonia cava showed effective antimicrobial activities. Especially, Morun albalinne showed the strongest growth inhibition on the isolated bacteria at $0.0025{\sim}0.0075%$.

• Food Science of Animal Resources
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• v.33 no.6
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• pp.772-780
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• 2013

The aim of this study was to investigate the effect of season and location on activities of enzyme produced by psychrotrophic bacteria isolated from raw milk located in Kyunggi region of South Korea. Agar diffusion and colorimetric methods were used for the lipase and protease activities of psychrotrophic bacteria. Intensities of dark blue and transparent ring around colony were compared for activity measurement. Nutrient agar with 1% skim milk added was employed for measuing protease activity. 14 strains of Arthrobacter russicus with lipase activity and 19 strains of Chryserobacterium shigense with protease activities were found to be present. It was found that Acinetobacter genomospecies 10 (match %: 99.90) isolated from B region in fall was the most lipolytic species, whereas Serratia liquefaciens (match %: 99.39) isolated from the same region in spring was the most proteolytic species. Growth curve of Acinetobacte and Serratia liquefaciens was a typical sigmoidal form. Lipase activity increased with incubation time, but its activity began to drop at stationary to motality phase. Optimum condition for incubation time, pH and temperature for extracellular lipase from Acinetobacter genomospecies 10 (match %: 99.90) was 12 h, 8.5, and $45^{\circ}C$, respectively. Extracellular protease from Serratia liquefaciens (match %:99.39) had the same optimum incubation time and pH as extracellular lipase, but optimum temperature was $35^{\circ}C$.

• Journal of Life Science
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• v.25 no.5
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• pp.507-514
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• 2015

D-Xylulose is phosphorylated to D-xylulose-5-phosphate by D-xylulose kinase before it enters glycolysis via the nonoxidative pentose phosphate pathway. A gene encoding a novel D-xylulose kinase (XK) from K. gwangalliensis strain SJ2 was sequenced and expressed in E. coli. The sequence of the isolated XK gene was 1,419 bp, encoding 472 amino acids. The XK protein was more closely related to the Arthrobacter phenanthrenivorans XK than to the Bifidobacterium catenulatum one, as reflected in the sequence identity (54.9% vs. 38.7%). The XK gene was subcloned into the pCold-II expression vector. The resulting plasmid was transformed into E. coli strain BL21 (DE3) cells and the expression of the recombinant XK protein was induced by the addition of IPTG. The resulting protein was expressed as a fusion protein of approximately 48 kDa containing a N-terminal six-histidine extension that was derived from the expression vector. The expressed protein was homogenized by affinity chromatography and showed enzymatic activity corresponding to D-xylulose kinase. XK enzyme kinetic studies with D-xylulose and ATP showed a Km of 250±20 μM and 1,300±50 μM, respectively. The results obtained from this study will provide a wider knowledge base for the characterization of D-xylulose kinase at the molecular level.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.2
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• pp.179-183
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• 1987

A series of laboratory experiments were conducted to find out the populations and identification of soil bacteria, fungi and their B/F ratio in the rhizosphere of intensively cultivatad hot-pepper, garlic, flower plants, chinese cabbage, and round onion. The results obtained are summarized as follows: 1. The number of bacteria, fungi and their B/F ratio are remarkably lower than that of normal paddy soils. 2. Nitrate reducers and bacteria which utilized simple sugars for their sole carbon source are predominated in the rhizosphere of intensively cultivated upland crops. 3. Alkaligenetic bacteria predominate in rhizosphere of garlic and tomato cultivated upland soils. 4. Genera of Pseudomonas, Xanthomonas, Bacillus, Arthrobacter, and Achromobacterium are the most common species in the rhizosphere of intensively cultivated upland crops and flower plants. 5. Phytotoxin producers such as Stachybotris sp. were identified in all rhizospheres of intensively cultivated upland crops and flower plants. 6. Most common and highest population of soil fungi were obtained for the genera of Penicillium, Humicola, Phoma and Aspergillus in the rhizosphere of intensively cultivated upland crops and flower plants.

• Journal of Life Science
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• v.25 no.2
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• pp.237-242
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• 2015

The use of calcite-forming bacteria (CFB) in crack remediation and durability improvements in construction materials creates a permanent and environmentally-friendly material. Therefore, research into this type of application is stimulating interdisciplinary studies between microbiology and architectural engineering. However, the mechanisms giving rise to these materials are dependent on calcite precipitation by the metabolism of the CFB, which raises concerns about possible hazards to cement-based construction due to microbial metabolic acid production. The aim of this study was to determine target microorganisms that possibly can have bio-corrosive effects on cement mortar and to assess multi-functional CFBs for their safe application to cement structures. The chalky test was first used to evaluate the $CaCO_3$ solubilization feature of construction sites by fungi, yeast, bacterial strains. Not all bacterial strains are able to solubilize $CaCO_3$, but C. sphaerospermum KNUC253 or P. prolifica KNUC263 showed $CaCO_3$ solubilization activity. Therefore, these two strains were identified as target microorganisms that require control in cement structures. The registered patented strains Bacillus aryabhatti KNUC205, Arthrobacter nicotianae KNUC2100, B. thuringiensis KNUC2103 and Stenotrophomonas maltophilia KNUC2106, reported as multifunctional CFB (fungal growth inhibition, crack remediation, and water permeability reduction of cement surfaces) and isolated from Dokdo or construction site were unable to solubilize $CaCO_3$. Notably, B. aryabhatti KNUC205 and A. nicotianae KNUC2100 could not hydrolyze cellulose or protein, which can be the major constituent macromolecules of internal materials for buildings. These results show that several reported multi-functional CFB can be applied to cement structures or diverse building environments without corrosive or bio-deteriorative risks.