• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.80.1-80
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• 2003

Several plant and microbial genes that could confer disease resistance in transgenic rice plants are being cloned and characterized. We are currently constructing transgenic rice lines that overexpress the gene products, such as a galactinol synthase, a defensin, and a bacterial ACC deaminase. Subtractive hybridization of a rice cDNA library constructed from the Xanthomonas oryzae-infected ice leaves resulted in isolation of many inducible cDNA clones including a elongation factor EF2, a oryzain alpha, a catalase, a aldehyde dehydrogenase, a S-adenosylmethionine synthetase, a caffeic acid O-methyltransferase, a glyceraldehyde-3-phosphate dehydrogenase, a light-regulated protein, nKY transcription factors, and a nucleotide diphosphate kinase. Some genes among those may be useful genetic sources for construction of disease resistant transgenic rice. Full lengths of the rice OsFIERG and a rice oryzain genomic clones were cloned, and serial deletion fragments of the promoter regions of these genes were fused with GUS reporter gene in pCAMBIA1201, respectively. Promoter activities of these constructs will be examined upon various stresses and Pathogen infections to obtain the pathogen specific inducible-promoter. This work was supported by a grant from BioGreen 21 Program, Rural Development Administration, Republic of Korea.

• Journal of Plant Biotechnology
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• v.44 no.2
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• pp.149-155
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• 2017

Bacterial blight in rice caused by Xanthomonas oryzae pv. oryzae (Xoo) greatly reduces the growth and productivity of this important food crop. Therefore, we sought to increase the resistance of rice to bacterial blight by using a NAC (NAM, ATAF, and CUC) transcription factor, one of the plant-specific transcription factors that is known to be involved in biotic/abiotic stress resistance. By isolating the OsNAC58 gene from rice and analyzing its biological functions related to Xoo resistance, phylogenetic analysis showed that OsNAC58 belongs to group III. To investigate the biological relationship between bacterial leaf blight (BLB) and OsNAC58 in rice, we constructed a vector for overexpression in rice and generated transgenic rice. The expression analysis resulting from use of RT-PCR showed that OsNAC58-overexpressed transgenic rice exhibited higher levels of OsNAC58 expression than wild types. Further, subcellular localization analysis using rice protoplasts showed that the 35S/OsNAC58-SmGFP fusion protein was localized in the nuclei. Thirteen OsNAC58-overexpressed transgenic rice lines, with high expression levels of OsNAC58, showed more resistant to Xoo than did the wild types. Together, these results suggest that the OsNAC58 gene of rice regulates the rice disease resistance mechanism in the nucleus upon invasion of the rice bacterial blight pathogen Xoo.

• Microbiology and Biotechnology Letters
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• v.32 no.3
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• pp.249-255
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• 2004

Chinese cabbage ('Baechu') Kimchi was fermented at the three different temperatures right after it was prepared. Samples were taken everyday for measuring bacterial populations, pH, and titratable acidity through the whole periods of fermentation up to 50 days. pH values and developed acidity were significantly affected by the fermenting temperatures of 4, 10, and $20^{\circ}C$, suggesting that different bacterial flora has been established by the temperatures exposed. The modified MRS agar containing vancomycin (300 $\mu$g/mL) was used for isolating the vancomycin-resistant LAB strains and 127 isolates were finally obtained. Of the LAB isolates, 13 isolates were subjected to the identification experiments based on the biochemical characteristics and the molecular-typing approach, an ITS-PCR, whether they belong to the genus Leuconostoc or not. The data obtained from API 50 CHL kit resulted that six isolates were identified as the members of Leuconostoc and six as Lactobacillus brevis strains except for a single isolate YKI 30-0401, which was not able to be identified because its biochemical traits were not matched to the database of API 50 CHL kit. It was noted that some isolates were distinct in a couple of some biochemical characteristics compared with those of the reference Leuconostoc species. To overcome the limitations experienced in the commercial identification products above, an ITS-PCR experiment was also conducted for the isolates, resulting that eight isolates belong to Leu. mesenteroides ssp. mesenteroides or dextranicum with a single band of 564 bp, and four to L. brevis strains. The ITS-PCR profiles clearly differentiated the closely-related LAB isolates for which same results were obtained by the biochemical method. This molecular approach, however, failed to produce the amplicons for the YKI 20-1003, leaving the strain unidentified. Judging from the identification data obtained in the Kimchi fermented at $4^{\circ}C$ or $10^{\circ}C$, Leuconostoc spp. including Leu. mesenteroides/dextranicum were likely predominant species in the earlier stage and L. brevis occurred at the high level through the whole period. By contrast, L. brevis, as one of the major flora, possibly lead the fermentation from the beginning in the Kimchi fermented at $20^{\circ}C$.}C$.

• Pediatric Infection and Vaccine
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• v.28 no.2
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• pp.82-91
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• 2021

Background: The purpose of this study was to investigate the association between antibiotic use and the antimicrobial resistance of gram-negative bacteria isolated from blood cultures in a pediatric population. Methods: From January 2014 to June 2018, the antibiotic resistance pattern of Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa obtained from bacteremic patients aged ≤18 years hospitalized at Asan Medical Center Children's Hospital was analyzed and the parenteral antibiotic consumption data were retrieved. Results: During the study period, the blood culture was positive for K. pneumoniae (6.4%; 105/1,628), E. coli (5.6%; 91/1,628), P. aeruginosa (3.3%; 54/1,628), and A. baumannii (2.5%; 41/1,628), and the extended-spectrum antibiotic resistance rate of gram-negative bacteria was consistently high. The overall resistance rate of E. coli and K. pneumoniae to extendedspectrum cephalosporin was 49.3% and 54.4%, respectively. Carbapenem-resistant E. coli was first detected in 2014; its overall resistance rate to carbapenem was 5.3%. There was a linear correlation between the usage of 3rd generation cephalosporin and the resistance of A. baumannii (r²=0.96, P=0.004) and carbapenem usage and the resistance of K. pneumoniae (r²=0.79, P=0.045). Conclusions: A positive linear correlation was observed between antibiotic resistance and the corresponding antibiotic usage in 3rd generation cephalosporin resistant A. baumannii and carbapenem resistant K. pneumoniae. The judicious use of antibiotics in healthcare settings is important to minimize selection for extended-spectrum β-lactamase (ESBL) and carbapenem resistance in gram-negative bacteria.

• FLOWER RESEARCH JOURNAL
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• v.18 no.1
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• pp.1-8
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• 2010

Sensitivities of PLBs of four Phalaenopsis cultivars, P. 'Taisuco Windian', P. 'Nancy Amour', P. 'Pink Twilight' and P. 'Taipei Gold' to kanamycin, spectinomycin and hygromycin at different concentrations (0, 25, 50, 100, 200, and $400mg{\cdot}L^{-1}$) were examined. Hygromycin was favorable for selecting the transformants in the genetic transformation of Phalaenopsis as PLBs of four cultivars were all dead at even $25mg{\cdot}L^{-1}$ hygromycin. Responses of PLBs of P. 'Maki Watanabe' and P. 'Brother Lawrence' to DL-phosphinothricin (PPT) were determined at different concentrations (0, 0.1. 0.25, 0.5, 1.0, 2.0, 2.5, and $5.0mg{\cdot}L^{-1}$) and $0.5mg{\cdot}L^{-1}$ PPT was thought to be suitable for selecting the transformants of Phalaenopsis. The optimum conditions for Agrobacterium cocultivation with Phalaenopsis PLBs were examined using a two-step cocultivation method in Dtps. 'City Girl' and A. tumefaciens LBA4404. In the first infection period in a 1 : 10 suspension of Agrobacterium to a VW medium, 1 hr infection showed the highest PLB survival ratio. And then, PLBs were cocultivated with a bacterial strain and a 3-day cocultivation period was better for Phalaenopsis PLBs than a prolonged period. Agrobacterium tumefaciens strains LBA4404 (pTOK233) and EHA105 (pGA643) were used to compare their efficiency on the genetic transformation of Phalaenopsis PLBs. The PLBs infected with EHA105 survived more than those infected with LBA4404 after two days in a dark condition and two weeks in light condition on a selective medium. About 1,000 PLBs for each of P. 'Maki Watanabe' and P. 'Brother Lawrence', and each bacterial strain of AGL1 (pCAMBIA3301) and LBA4404 (pTOK233) were used for the regeneration of transgenic plants. The bacterial strain AGL1 had a higher genetic transformation efficiency than LBA4404, with no significant difference between cultivars. In this study, 11 hygromycin-resistant plantlets and 32 PPT-resistant plantlets were produced, but these putative transgenic plantlets need further examinations.

• Korean Journal of Environmental Biology
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• v.35 no.4
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• pp.694-705
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• 2017

The aim of this study was to isolate and identify marine bacterium with anti-methicillin-resistant Staphylococcus aureus (MRSA) activity, and to purify the anti-MRSA compound, as well as to determine its activity and synergistic effects. Among the marine bacteria isolated in this study, the YJ-1 isolate had the strongest anti-MRSA activity. The YJ-1 isolate was identified on the basis of its biochemical characteristics and an analysis of 16S rRNA gene sequences. The YJ-1 isolate showed over 99.2% homology with Pseudomonas stutzeri, and was designated as a Pseudomonas sp. YJ-1. The optimal culture conditions were $25^{\circ}C$ and initial pH 7.0. For the purification of the anti-MRSA compounds, the YJ-1 was cultured in Pa PES-II medium, and the culture filtrates were extracted by ethyl acetate, hexane, and 80% MeOH. The 80% MeOH fraction was separated by a $C_{18}$ ODS column, silica gel chromatography and a reverse phase HPLC, to yield three anti-MRSA agents, the MR1, MR2, and MR3 compounds. When the MR1 compound of $250{\mu}g\;mL^{-1}$ concentration was applied to the MRSA cells, over 95% of bacterial cells was killed within 48 hr. Compared with vancomycin and ampicillin, the MR1 compound showed significant anti-MRSA activity. In addition, the anti-MRSA activity was increased by dose and time dependent manners. Furthermore, the combination of an MR1 compound with vancomycin produced a more rapid decrease in the MRSA cells than did the MR1 compound alone. Taken together, our results suggest that the Pseudomonas sp. YJ-1 and its anti-MRSA compounds could be employed as a natural antibacterial agent in MRSA infections.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.82-87
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• 2016

Enterotoxigenic Bacteroides fragilis (ETBF) produces enterotoxins known to be a virulence factor. Three isotypes of the B. fragilis toxin (BFT) gene have been identified: bft-1, bft-2, and bft-3. We investigated the presence of bft isotypes in clinical B. fragilis isolates and the antimicrobial resistance of BFT-negative and BFT-positive isolates. Overall, 537 B. fragilis isolates were collected from extraintestinal specimens over 8 years (2006~2013) from a university hospital in Korea. Samples were analyzed by multiplex PCR to identify the bft gene isotypes. Additionally, the antimicrobial susceptibility of 107 B. fragilis isolates (74 BFT-negative and 33 BFT-positive) was examined by the CLSI agar dilution method. PCR revealed a total bft gene detection rate of 30%, while 33% and 29% of blood and other extraintestinal isolates contained the gene, respectively. Among ETBF isolates, the most common isotype was bft-1 gene, followed by bft-2 and bft-3 (bft-1 77%, bft-2 14%, bft-3 9%). Resistance rates (%) for BFT-negative and positive isolates differed in response to various antimicrobial agents, with 3%, 5%, 1% and 38% of BFT-negative isolates and 3%, 6%, 3% an 42% of BFT-positive isolates being resistant to piperacillin-tazobactam, cefoxitin, imipenem, and clindamycin, respectively. Interestingly, neither BFT-negative nor positive isolates showed antimicrobial resistance to chloramphenicol and metronidazole. Overall, the proportion of ETBF from blood was similar to that of other extraintestinal sites and the bft-1 gene was the predominant isotype. Higher antimicrobial resistance rates were found in BFT-positive isolates than BFT-negative isolates, but these differences were not statistically significant.

• Korean Journal of Breeding Science
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• v.41 no.3
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• pp.314-318
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• 2009

A new rice cultivar "Jinbaek" carrying Xa3 and xa5 was derived from the cross between 'HR15204-38-3' with xa5 gene resistant to bacterial blight K1, K2, K3 and K3a, and F1 plant derived from the cross between Junam and Sindongjin with Xa3 gene. "Jinbaek" has approximately 125 days of growth duration from transplanting to harvesting in the west-southern coastal and Honam plain of Korea. Culm length of "Jinbaek" is 71 cm. In reaction to biotic stresses, it shows moderate resistance to blast, and wide spectrum resistance to bacterial blight pathogen, K1, K2, K3, and K3a but susceptible to rice stripe virus and blast. The milled rice of "Jinbaek" exhibits translucent, relatively clear non-glutinous endosperm and midium short grain. It has lower amylose content (18.8%) and protein content (6.2%) compared with Nampyeong. The milled rice yield of this cultivar was 5.30 MT/ha in local adaptability test of three years from 2006 to 2008. This cultivar would be adaptable to the bacterial blight-prone area in the south-western coast and Honam plain of Korea.

• Korean Journal of Breeding Science
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• v.51 no.3
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• pp.263-276
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• 2019

'Sinjinbaek' is a bacterial blight (BB)-resistant, mid-late maturing rice cultivar with high grain quality. To diversify the resistance genes and enhance the resistance of Korean rice cultivars against BB, 'Sinjinbaek' was developed from a cross between 'Iksan493' (cultivar name 'Jinbaek') and the F₁ cross between 'Hopum' and 'HR24670-9-2-1' ('HR24670'). 'Jinbaek' is a BB-resistant cultivar with two BB resistance genes, Xa3 and xa5. 'Hopum' is a high grain quality cultivar with the Xa3 resistance gene. 'HR24670' is a near-isogenic line that carries the Xa21 gene, a resistance gene inherited from a wild rice species O. longistaminata, in the genetic background of japonica elite rice line 'Suweon345'. 'Sinjinbaek' was selected through the pedigree method, yield trials, and local adaptability tests. Using bioassay for BB races and DNA markers for resistance genes, three resistance genes, Xa3, xa5, and Xa21, were pyramided in the 'Sinjinbaek' cultivar. 'Sinjinbaek' exhibited high-level and broad-spectrum resistance against BB, including the K3a race, the most virulent race in Korea. 'Sinjinbaek' is a mid-late maturing rice cultivar tolerant to lodging. It has multiple disease resistance against BB, rice blast, and stripe virus. The yield of 'Sinjinbaek' was similar to that of 'Nampyeong'. 'Sinjinbaek' showed excellent grain appearance, good taste of cooked rice, and enhanced milling performance, and we concluded that it could contribute to improving the quality of BB-resistant cultivars. 'Sinjinbaek' was successfully introgressed with the Xa21 gene without the linkage drag negatively affecting its agronomic characteristics. 'Sinjinbaek' improved the resistance of Korean rice cultivars against BB by introgression of a new resistance gene, Xa21, as well as by pyramiding three resistance genes, Xa3, xa5, and Xa21. 'Sinjinbaek' would be suitable for the cultivation in BB-prone areas since it has been used in breeding programs for enhancing plants' resistance to BB (Registration No. 7273).

• Journal of Mushroom
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• v.14 no.3
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• pp.81-89
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• 2016

White button mushroom (Agaricus bisporus) is the most widely consumed mushroom in the world, and domestic consumption is increasing owing to expansion of the westernized diet in recent years. Before 2000, most Korean mushroom farmers cultivated foreign varieties, but recently, Korean breeders are developing hybrid strains using molecular breeding tools. To produce a better mushroom cultivar, we evaluated some traits of button mushroom Agaricus bisporus strains. Mycelial growth rate at different culture temperatures was investigated by 25>20>15>30>$10^{\circ}C$. Recently developed domestic varieties had superior mycelial growth rate compared to the traditionally grown species. In particular, the ASI1338 strain showed excellent mycelial growth rate at different temperatures. Further, we confirmed that ASI1007, ASI1085, ASI1310, ASI1339 were strongly resistant to bacterial brown blotch, whereas ASI1053, ASI1103, ASI1140, ASI1146, ASI1177, ASI1183, ASI1195, ASI1321, ASI1331, ASI1336 were relatively weakly resistant. The average number of days for 16.5, and that for harvest was 5.7; the average yield was 142.7 g/2-kg bag. Mycelial growth rates at 10, 15, 20, $25^{\circ}C$ were similar, but that at $30^{\circ}C$ was lower. The mushroom yield was highly correlated with the number of days for pinheading and harvest.