• Journal of Life Science
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• v.25 no.12
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• pp.1408-1414
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• 2015

In this study, to retain a stable bacterial inoculant, Bacillus strains showing antifungal activity were screened. The improved production, antifungal mechanism, and stability of the antifungal metabolite by a selected strain, AF4, a potent antagonist against phytopathogenic Botrytis cinerea, were also investigated. The AF4 strain was isolated from rhizospheric soil of hot pepper and identified as Bacillus subtilis by phenotypic characters and 16S rRNA gene analysis. Strain AF4 did not produce antifungal activity in the absence of a nitrogen source and produced antifungal activity at a broad range of temperatures (25-40℃) and pH (7-10). Optimal carbon and nitrogen sources for the production of antifungal activity were glycerol and casein, respectively. Under improved conditions, the maximum antifungal activity was 140±3 AU/ml, which was higher than in the basal medium. Photomicrographs of strain AF4-treated B. cinerea showed morphological abnormalities of fungal mycelia, demonstrating the role of the antifungal metabolite. The B. subtilis AF4 culture exhibited broad antifungal activity against several phytopathogenic fungi. The antifungal activity was heat-, pH-, solvent-, and protease-stable, indicating its nonproteinous nature. These results suggest that B. subtilis AF4 is a potential candidate for the control of phytopathogenic fungi-derived plant diseases.

• Journal of Life Science
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• v.30 no.2
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• pp.156-161
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• 2020

Since industrialization, the production and utilization of various chemicals has contributed to improving the quality of our lives, but the subsequent discharge of massive waste is inevitable, and environmental pollution is becoming more serious every day. Exposure to chemicals as a result of environmental pollution is having a negative effect on human health and the ecosystem, and cleaning up the polluted environment that can affect our lives is a very important issue. Toxic aromatic compounds have been detected frequently in soil, groundwater, and wastewater because of the extensive use of oil products, and phenol, which is used to produce synthetic resins, textiles, and dyes, is one of the major pollutants, along with insecticides and preservatives. Phenol can cause dyspnea, headache, vomiting, mutation, and carcinogenesis. Phenol-degrading bacterium DWB-1-8 was isolated from the activated sludge of textile wastewater; this strain was identified as Comamonas testosteroni by 16S rRNA gene sequencing. The optimal culture conditions for the cell growth and degradation of phenol were 0.7% K₂HPO₄, 0.6% NaH₂PO₄, 0.1% NH₄NO₃, 0.015% MgSO₄·7H₂O, 0.001% FeSO₄·7H₂O, an initial pH of 7, and a temperature of 30℃. The strain was also able to grow by using other toxic compounds, such as benzene, toluene, or xylene (BTX), as the sole source of carbon.

• Journal of Life Science
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• v.19 no.4
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• pp.429-435
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• 2009

Oxidative stress is a consequence of an imbalance of the defense system against cellular damage generated by reactive oxygen species (ROSs) such as superoxide anions (menadione; MD). Most organisms have evolved a variety of defense systems to protect cells from adverse conditions. In order to evaluate stress tolerance against oxidative stress generating MD, comparative analyses of antioxidant capacity, or free radical scavenger ability, were performed between S. cerevisiae KNU5377 (KNU5377) and three wild-type S. cerevisiae strains. In a medium containing 0.4 mM MD, the KNU5377 strain showed higher cell viability and antioxidant ability, and contained higher levels of trehalose, superoxide dismutase, thioredoxin system, glucose-6-phosphate dehydrogenase, and some heat shock proteins. The KNU5377 strain also produced a lower level of oxidative stress biomarker than the other three yeast strains. These results indicate that S. cerevisiae KNU5377 has a higher level of tolerance to oxidative stress due to the increased expression of cell rescue proteins and molecules, thus alleviating cellular damage more efficiently than other S. cerevisiae strains.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.329-335
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• 2014

This study was performed to study characteristics of new zoysiagarass cultivar 'Green Ever' (Plant Variety Protection Application no. 2014 - 02). 'Green Ever' was developed by selection breeding among 100 native zoysiagrasses collected in South Korea. 'Green Ever' showed specific bands (1.48 kb with OPC14 and 1.05 kb with OPD5) which were distinct from 'Anyang Joonggi' or 'Dongrae Koryogi' in RAPD analysis. 'Green Ever' was classified as Z. matrella in morphological evaluations including plant height ($6.8{\pm}0.5cm$), leaf width ($2.0{\pm}0.1mm$), height of lowest leaf ($1.9{\pm}0.1cm$) and seed length ($3.0{\pm}0.1mm$), which was similar with morphological characteristics of 'Dongrae Koryogi'. Turf quality, shoot density and chlorophyll content of 'Green Ever' were higher than them of 'Anyang Joonggi' and 'Dongrae Koryogi' under intensive management such as fairway on golf course, especially shoot densities of 'Green Ever' were excellent higher than 'Anyang Joonggi' and 'Dongrae Koryogi' during experimental periods. It could be extensively used in fairway, teeing ground of golf courses and landscape garden after further study about various environmental adaptabilities such as winter kill, wear tolerance etc.

• Korean Journal of Microbiology
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• v.49 no.2
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• pp.156-164
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• 2013

Actinomycetes produce diverse secondary metabolites which have the primary importance in medicine, agriculture and food production, and key to this is their ability to interact with other organisms in natural habitats. In this study, we have investigated the taxonomical and functional diversity of actinomycetes in fecal sample of rhinoceros beetle larvae (Allomyrina dichotoma L.) by using culture-dependent and -independent approaches. For the culture-independent approach, the community DNA was extracted from the sample and 16S rRNA genes of actinomycetes were amplified using actinomycetes-specific PCR primers. Thirty-seven clones were classified into 15 genera and 24 species of actinomycetes. For the culture-dependent approach, 53 strains were isolated from larval feces, of which 27 isolates were selected based on morphological characteristics. The isolates were classified into 4 genera and 14 species, and 24 isolates (89%) were identified as the genus Streptomyces. Many of the representative isolates had antimicrobial activities against plant pathogenic fungi and Gram-positive bacteria. In addition, most of the isolates (78%) showed biochemical properties to hydrolyze cellulose and casein. The results demonstrated that diverse and valuable actinomycetes could be isolated from insect fecal samples, indicating that insect guts can be rich sources for novel bioactive compounds.

• Journal of Life Science
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• v.21 no.10
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• pp.1487-1493
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• 2011

E. tarda, a fish pathogen, can survive in seawater under relatively high salt conditions as well as in fish under physiological salt conditions. Bacterial growth under different salt concentrations may influence the expression of genes involved in bacterial structure and physiology. The growth rate of E. tarda culture in high salt (3.5% NaCl) was similar to that in low salt (1.0% NaCl, physiological salt concentration). Interestingly, the strain moved much faster in low salt conditions than in high salt conditions. Electron microscopic observation demonstrated that the bacterial cells grown in high salt had less or no flagellation. Obvious flagellation was observed in the parental strain E. tarda CK41 grown in low-salt condition. Two putative genes coding flagellin were identified in the E. tarda genome sequences. The amino acid sequence comparison of each gene revealed 93% identities. A flagellin gene was PCR amplified and cloned into a cloning vector. Using an E. coli protein expression system, a part of flagellin protein was overexpressed. Using the purified protein, an anti-flagellin antibody was raised in the rabbit. Immunoblot analyses with flagellin specific antibody demonstrated that E. tarda CK41 expressed falgellin in low salt conditions, which is consistent with the results seen in motility assay and microscopic observation. This is the first report of salt regulated flagella expression in E. tarda.

• Korean Journal of Microbiology
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• v.50 no.2
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• pp.119-127
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• 2014

The affiliations and physiological characteristics of culturable bacteria isolated from the sediments of Ross Sea, Antarctica were investigated. Sixty-three isolates obtained by cultivation were grouped into 21 phylotypes affiliated with the phyla Actinobacteria and Bacteroidetes and with the classes Alphaproteobacteria and Gammaproteobacteria by phylogenetic analysis of 16S rRNA gene sequences. Based on phylogenetic analysis (<98.65% sequence similarity), approximately 49% of total isolates represented potentially novel species or genus. Among them, extracellular protease, lipase, and exopolysaccharide activities at $10^{\circ}C$ or $20^{\circ}C$ were detected in approximately 46%, 25%, and 32% of the strains, respectively. Forty-three isolates produced at least one type of extracellular material and 21 of them produced at least two extracellular protease, lipase, and/or exopolysaccharides. Our findings indicate that culturable bacterial diversity present within the marine sediments of Ross Sea, Antarctica may contribute to the hydrolysis of the major organic constituents which is closely related with carbon and nitrogen cycling in this environment.

• Korean Journal of Ecology and Environment
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• v.50 no.2
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• pp.266-274
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• 2017

We surveyed the habitat use and food materials of the endangered Swan Goose (Anser cygnoides) during the wintering period at the Seocheon tidal flat. The bird wintered about six months from October 2014 to early April 2015 at the flat. They showed a remarkable change in choosing their feeding habitat and prey. They stayed entirely at sedge grass patches on Songrim tidal flat during the early wintering period (October), while after November they gradually moved to Janggu bay and used rice paddy fields as well as sedge patches on the tidal flats as their feeding site. The dietary analysis showed the sedge grass (Bolboschoenus sp., Cyperaceae) was the main dietary source during the entire wintering period. Interestingly, the proportion of Cyperaceae on feces decreased slightly over wintering time, while the proportion of Fabaceae increased relatively since November. These results suggest that the Swan Geese switched their habitat and food sources in response to the change of food availability. The Seocheon tidal flat area is the important wintering site for Swan Geese and sedge grass patches in the area need to be managed as the main feeding area for the wintering Swan Geese.

• Journal of Life Science
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• v.28 no.3
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• pp.376-387
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• 2018

Among a variety of environmental stresses heat, cold, chilling, high salt, drought, and so on exposed to plants, drought stress has been reported as a crucial factor to adversely affect the growth and productivity of plants. Therefore, to understand the mechanism for the drought stress signal transduction pathway in plants is more helpful to develop useful crops that display the enhanced tolerance against drought stress, and to expand crop growing areas. The signal transduction pathway for the drought stress in plants is largely categorized into two types; ABA-dependent pathway and ABA-independent pathway. It has been reported that two transcription factors, AREB/ABF and DREB2, play predominant roles in ABA-dependent and ABA-independent pathways, respectively. In addition to transcriptional regulation mediated by AREB/ABF and DREB2 transcription factors, post-translational modification (such as phosphorylation and ubiquitination) and epigenetic control are importantly involved in the signal transduction for drought stress. In this paper, we review current understanding of signal transduction pathway on drought stress in plants, especially focusing on the biological roles of a variety of signaling components related to drought stress response. Further understanding the mechanism of drought resistance in plants through this review will be useful to establish theoretical basis for developing drought tolerant crops in the future.

• Journal of Plant Biotechnology
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• v.44 no.1
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• pp.12-18
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• 2017

The dried root of Angelica species is used in traditional Chinese medicine in East Asia, particularly in Korea, China and Japan. Since the plant origin differs in these countries, they are often misused or adulterated in the commercial markets, resulting in distrust among the consumers. Enormous efforts have therefore been focused to distinguish the origin for the Angelica genus, by using morphological or cytogenetical analyses, and chemical markers based on biochemical analyses of secondary metabolites. DNA is considerably stable against different cultivation conditions, and to treatment and processing after harvesting of plants. Hence, several researches have been filed for the development of molecular markers, based on the single nucleotide polymorphisms in specific regions of DNA. However, there are several obstacles for application in the commercial markets, concerning the reproducibility, accuracy, sensitivity, and rapidity of these tests. In this review, we summarize the research achievements that help classify the origin of Angelica species, in particular, Angelica gigas Nakai. A. sinensis(oliv.) Diels, A. acutiloba Kitag., and A. acutiloba var. sugiyamae Hikino. Further researches are required for practical applications.