• Journal of Microbiology and Biotechnology
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• v.22 no.12
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• pp.1605-1612
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• 2012

The present study concerned the identification and characterization of a novel bacterial strain isolated from entomopathogenic nematodes collected from different regions in Korea. The bacterial isolate M1021 was Gramnegative, bioluminescent, and produced red colonies on MacConkey agar medium. A rod-shaped structure was confirmed by the electron micrograph. Fatty acid composition was analyzed by using the Sherlock MIDI system. The identification was further supported by 16S rDNA sequence analysis, which revealed 96-99% sequence homology with strains of Photorhabdus temperata. The location of the isolated strain of P. temperata in the phylogenetic tree was confirmed and it was named P. temperata M1021. P. temperata M1021 exhibited catalase, protease, and lipase activities when grown on appropriate media supplemented with respective substrates. The culture of P. temperata M1021 exhibited insecticidal activity against the larvae of Galleria mellonella and the activity was the highest after 3-4 days of cultivation with agitating at $28^{\circ}C$ under 220 rpm. Antibacterial activity was also observed against Salmonella Typhimurium KCTC 1926 and Micrococcus luteus KACC 10488.

• KSBB Journal
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• v.28 no.3
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• pp.165-169
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• 2013

In this study, 52 ureolytic bacterial strains were newly isolated from various environments. From these, 2 strains (TB-15 and TB-22) were selected based on their high urease activity. XRD spectra clearly showed presence of various sequestration products such as calcite and strontianite in samples. TB-22 showed 20~30% higher survivability upon Sr concentration (20 mM) than Sporosarcina pasteurii KCTC 3558. TB-15 and TB-22 showed 80~90% higher survivability at pH 6 than S. pasteurii. The results demonstrated that the 2 isolates colud be good candidates for the bioremediation of Sr contaminated sites.

• Journal of Microbiology
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• v.43 no.5
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• pp.456-462
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• 2005

More than seventy strains of aerobic bacteria showing ${\beta}$-glucosidase activity were isolated from a ginseng field, using a newly designed Esculin-R2A agar, and identified by their 16S rRNA gene sequences. Of these microorganisms, twelve strains could convert the major ginsenoside, $Rb_1$, to the pharmaceutically active minor ginsenoside Rd. Three strains, Burkholderia pyrrocinia GP16, Bacillus megaterium GP27 and Sphingomonas echinoides GP50, were phylogenetically studied, and observed to be most potent at converting ginsenoside $Rb_1$ almost completely within 48 h, as shown by TLC and HPLC analyses.

• Proceedings of the Microbiological Society of Korea Conference
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• 2001.11a
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• pp.157-163
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• 2001

Mycolic acid-containing gram-positive bacteria, so called nocardioform actinomycetes, have become a great interest to environmental microbiologists due to their metabolic versatility, multidegradative capacity and potential for bioremediation of priority pollutants. For example, Rhodococcus rhodochrous N75 was able to metabolize 4-methy1catechol via a modified $\beta$-ketoadipate pathway whereby 4-methylmuconolactone methyl isomerase catalyzes the conversion of 4-methylmuconolactone to 3-methylmuconolactone in order to circumvent the accumulation of the 'dead-end' metabolite, 4-methylmuconolactone. R. rhodochrous N75 has also shown the ability to transform a range of alkyl-substituted catechols to the corresponding muconolactones. A novel 3-methylmuconolactone-CoAsynthetase was found to be involved in the degradation of 3-methylmuconolactone, which is not mediated in a manner analogous to the classical $\beta$-ketoadipate pathway but activated by the addition of CoA prior to hydrolysis of lactone ring, suggesting that the degradative pathway for methylaromatic compounds by gram-positive bacteria diverges from that of proteobacteria. Mycobacterium sp. Strain PYR-l isolated from oil-contaminated soil was capable of mineralizing various polyaromatic hydrocarbons (PAHs), such as naphthalene, phenanthrene, pyrene, fluoranthrene, 1-nitropyrene, and 6-nitrochrysene. The pathways for degradation of PAHs by this organism have been elucidated through the isolation and characterization of chemical intermediates. 2-D gel electrophoresis of PAH-induced proteins enabled the cloning of the dioxygenase system containing a dehydrogenase, the dioxygenase small ($\beta$)-subunit, and the dioxygenase large ($\alpha$)-subunit. Phylogenetic analysis showed that the large a subunit did not cluster with most of the known sequences except for three newly described a subunits of dioxygenases from Rhodococcus spp. and Nocardioides spp. 2-D gel analysis also showed that catalase-peroxidase, which was induced with pyrene, plays a role in the PAH metabolism. The survival and performance of these bacteria raised the possibility that they can be excellent candidates for bioremediation purposes.

• Korean Journal of Food Science and Technology
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• v.23 no.6
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• pp.689-694
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• 1991

Jangsu, a Korean ancient non-alcoholic beverage made by lactic acid fermentation of cooked rice, was prepared and the microbial characteristics were investigated. The periodic removal of fermented product and the addition of newly made cooked rice and cold water as new substrate enhanced the growth of lactic acid forming bacteria but supressed the growth of proteolytic bacteria. The important microorganisms in jangsu were Lactobacillus, Lactococcus, Pediococccus and Leuconostoc species. Lactococcus thermophilus, Lactobacillus coryniformis and Leuconostoc mesenteroides were identified. The isolated strains were cultivated and used as starter culture of jangsu. Some useful strains were selected which were able to produce acceptable flavor and sufficient amount of acid lowering the pH to near 4.0.

• BMB Reports
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• v.40 no.6
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• pp.881-887
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• 2007

It is a hot clinical issue whether newly approved antimicrobial agents such as daptomycin, linezolid, quinupristin/dalfopristin (synercid) and tigecycline are active enough to be used for infections caused by vancomycin resistant bacteria. We performed susceptibility tests for mupirocin, which is in widespread clinical use in Korea, and four new antimicrobials, daptomycin, linezolid, quinupristin/dalfopristin and tigecycline, against vancomycin-resistant Enterococcus faecalis and Enterococcus faecium isolated from Korean patients in 1998 and 2005 to evaluate and compare the in vitro activity of these antimicrobials. Among these agents, quinupristin/dalfopristin, which is rarely used in hospitals in Korea, showed relatively high resistance to several vancomycin-resistant enterococci (VRE) isolated in 2005. Likewise, daptomycin, linezolid and tigecycline have not yet been in clinical use in Korea. However, our results showed that most of the 2005 VRE isolates were already resistant to linezolid and daptomycin (highest minimum inhibitory concentration (MIC) value >$100{\mu}g$/ml). Compared with the other four antimicrobial agents tested in this study, tigecycline generally showed the greatest activity against VRE. However, four strains of 2005 isolates exhibited resistance against tigecycline (MIC >$12.5{\mu}g$/ml). Almost all VRE were resistant to mupirocin, whereas all E. faecium isolated in 1998 were inhibited at concentrations between $0.8\sim1.6{\mu}g$/ml. In conclusion, resistances to these new antimicrobial agents were exhibited in most of VRE strains even though these new antibiotics have been rarely used in Korean hospitals.

• Food Engineering Progress
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• v.14 no.3
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• pp.263-270
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• 2010

An alkalophilic microorganism named DK-2386, which produces xylanase, was isolated from soil of Taejo-mountain, Cheonan-si, Chungnam, Korea. The isolated strain was characterized as Gram-positive, with size of 0.4${\times}$2.5 ${\mu}$m, spore forming, anaerobic, catalase positive, possessed with hydrolysis abilities of casein, starch, sodium carboxy methyl cellulose, and xylan, reduction of nitrate to nitrite, resistant against lysozyme, urease positive, and motility positive. The color of culture broth was reddish yellow. The strain DK-2386 was identified as Bacillus agaradhaerens by whole cell fatty-acid composition analysis and 16S rDNA sequence analysis. However, it was not identical to Bacillus agaradhaerens 40952 obtained from the Korean Culture Center of Microorganism in its colour of culture broth. Therefore, we have named the newly isolated strain as Bacillus agaradhaerens DK-2386.

• Journal of Microbiology and Biotechnology
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• v.32 no.11
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• pp.1416-1426
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• 2022

The need to discover new types of antimicrobial agents has grown since the emergence of antibiotic-resistant pathogens that threaten human health. The world's oceans, comprising complex niches of biodiversity, are a promising environment from which to extract new antibiotics-like compounds. In this study, we newly isolated Pseudomonas sp. NIBR-H-19 from the gut of the sea roach Ligia exotica and present both phenotypes and genomic information consisting of 6,184,379 bp in a single chromosome possessing a total of 5,644 protein-coding genes. Genomic analysis of the isolated species revealed that numerous genes involved in antimicrobial secondary metabolites are predicted throughout the whole genome. Moreover, our analysis showed that among twenty-five pathogenic bacteria, the growth of three pathogens, including Staphylococcus aureus, Streptococcus hominis and Rhodococcus equi, was significantly inhibited by the culture of Pseudomonas sp. NIBR-H-19. The characterization of marine microorganisms with biochemical assays and genomics tools will help uncover the biosynthesis and action mechanism of antimicrobial metabolites for development as antagonistic probiotics against fish pathogens in an aquatic culture system.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2159-2170
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• 2016

Many plant-pathogenic bacteria are dependent on quorum sensing (QS) to evoke disease. In this study, the population of QS and quorum quenching (QQ) bacteria was analyzed in a consecutive monoculture system of Pseudostellaria heterophylla. The isolated QS strains were identified as Serratia marcescens with SwrIR-type QS system and exhibited a significant increase over the years of monoculture. Only one QQ strain was isolated from newly planted soil sample and was identified as Bacillus thuringiensis, which secreted lactonase to degrade QS signal molecules. Inoculation of S. marcescens to P. heterophylla root could rapidly cause wilt disease, which was alleviated by B. thuringiensis. Furthermore, the expression of lactonase encoded by the aiiA gene in S. marcescens resulted in reduction of its pathogenicity, implying that the toxic effect of S. marcescens on the seedlings was QS-regulated. Meanwhile, excess lactonase in S. marcescens led to reduction in antibacterial substances, exoenzymes, and swarming motility, which might contribute to pathogensis on the seedlings. Root exudates and root tuber extracts of P. heterophylla significantly promoted the growth of S. marcescens, whereas a slight increase of B. thuringiensis was observed in both samples. These results demonstrated that QS-regulated behaviors in S. marcescens mediated by root exudates played an important role in replanting diseases of P. heterophylla.