• 한국미생물·생명공학회지
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• 제18권3호
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• pp.268-272
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• 1990

Zymomonas mobilis의 알코올 탈수소 효소 유전자가 클로닝된 대장균 형질전환체의 세포 추출물로부터 알코올 탈수소 효소를 분리정제하였다. 형질전환된 Escherichia coli(pADS93)가 생산하는 Z.mobilis 유전자 유래의 알코올 탈수소 효소는 분자량이 40,000인 동일한 4개의 subunits로 구성된 tetramer임이 밝혀졌으며 이것은 Z.mobilis의 세포 추출물로부터 분리한 알코올 탈수소 효소와 동일하였다. 이 효소의 정반응(ethanol 산화)은 pH의 영향을 많이 받으며 pH는 10.0이었고 역반응(acetaldehyde 환원)에서는 최적의 pH가 7.5-8.5 이었지만 pH에 따라 크게 영향을 받지는 않았다.

• 대한미생물학회지
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• 제11권1호
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• pp.1-11
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• 1976

Escherichia coli(ATCC 11115)에 실험실등에서 상용하는 여러가지 항균제를 시간별로 처리, 그 변화양상을 전자현미경으로 관찰한 바 그 결과를 요약하면 다음과 같다. 1) 대조군은 3층의 단일막으로 형성된 세포벽에 둘러쌓여 있으며 세포질은 전자밀도가 낮은 nucleoid와 ribosme들이 산재하여 있음을 관찰할 수 있었다. 2) 70% ethanol용액 처리군은 핵물질을 관찰할 수 없었고 세포질은 세포 중앙부로 응집되어 있었으며 세포벽의 외부에서는 bleb 들을 관찰 할 수 있었다. 3) 3% $H_2O_2$ 용액 처리군은 세포내용물의 변화는 70% ethanol 처리군과 대동소이(大同小異)하였으나 세포벽에서는 심한 굴곡현상이 관찰되었다. 4) 5% lysol 용액처리군은 세포질 및 핵물질 부위가 완전히 구분되어 나타났으며 세포질내의 ribosome과립들은 시간이 경과할수록 그 응집현상이 심하였고 세포 외부에는 ribosome 양 과립들이 부착하고 있음이 관찰되었다. 5) 1% DDEGH 용액 처리군은 세포질의 응집 및 세포막과 세포벽이 뚜렷이 관찰되지 않았으며 세포외부에 세포내용물과 동일한 물질로 생각되는 물질이 부착되어 있음을 관찰할 수 있었다. 6) 고압멸균 처리군은 세포막 및 세포벽의 파괴, 탈락 및 세포내용물의 유출현상이 관찰되었다.

• 센서학회지
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• 제23권1호
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• pp.35-41
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• 2014

Microbes have been used extensively in various fields of researches and industries but has not been used widely for microfluidic biosensor applications because it is difficult to immobilize properly to a small space. Therefore, we developed a microbial immobilization method for microfluidic devices using single-walled nanotubes and dielectrophoretic force. Single-walled nanotubes and Escherichia coli were aligned between two cantilever electrodes by a positive dielectrophoretic force resulting in a film of single-walled nanotubes with attached Escherichia coli. The optimal condition of film formation without a cell lysis was investigated. Diameter of single-walled nanotubes and electric field (intensity and duration of application) had an effect on the cell viability. On the other hand, the cell concentration of the suspension did not affect the cell viability. Paraoxon was detected using single-walled nanotubes film with attached Escherichia coli that expressed organophosphorus hydrolase. This film which is suspended from the substrate showed faster response time than sensors that are not suspended from the substrate.

• Journal of Animal Science and Technology
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• 제62권4호
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• pp.543-552
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• 2020

For efficient prevention and treatment of enteric colibacillosis, understanding about latest virulence factors and antimicrobial resistance of Escherichia coli is essentially needed. The aim of this study was to survey antimicrobial resistance and determine the prevalence of fimbriae and enterotoxin genes among 118 pathogenic E. coli isolates obtained from Korean pigs with diarrhea between 2016 and 2017. The genes for the toxins and adhesins were amplified by polymerase chain reaction (PCR). The susceptibility of the E. coli isolates to antimicrobials were tested using the standard Kirby-Bauer disk diffusion method. The most prevalent fimbrial antigen was F18 (40.7%), followed by F4 (16.9%), and the most prevalent combinations of toxin genes were Stx2e (21.2%), STb:EAST-1 (19.5%), and STa:STb (16.9%), respectively. Among the pathotypes, enterotoxigenic E. coli (ETEC) was the most predominant (67.8%), followed by Shiga-toxin producing E. coli (STEC, 23.7%). We confirmed high resistance rates to chloramphenicol (88.1%), tetracycline (86.4%), streptomycin (86.4%), and ampicillin (86.4%). And the majorities of isolates (90.7%) showed multi-drug resistance which means having resistance to 3 or more subclasses of antimicrobials. Results of this study can be a source of valuable data for investigating the epidemiology of and control measures for enteric colibacillosis in Korean piggeries.

• Journal of Microbiology
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• 제45권1호
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• pp.69-74
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• 2007

Escherichia coli is a clonal species, and occurs as both commensal and pathogenic strains, which are normally classified on the basis of their O, H, and K antigens. The O-antigen (O-specific polysaccharide), which consists of a series of oligosaccharide (O-unit) repeats, contributes major antigenic variability to the cell surface. The O-antigen gene cluster of E. coli O66 was sequenced in this study. The genes putatively responsible for the biosynthesis of dTDP-6-deoxy-L-talose and GDP-mannose, as well as those responsible for the transfer of sugars and for O-unit processing were identified based on their homology. The function of the wzy gene was confirmed by the results of a mutation test. Genes specific for E. coli O66 were identified via PCR screening against representatives of 186 E. coli and Shigella O type strains. The comparison of intergenic sequences located between galF and the O-antigen gene cluster in a range of E. coli and Shigella showed that this region may perform an important function in the homologous recombination of the O-antigen gene clusters.

• Archives of Pharmacal Research
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• 제21권3호
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• pp.305-309
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• 1998

Human cytochrome P450 1A2 is one of the major cytochrome P450s in human liver. It is known to be capable of activating a number of carcinogens such as arylamines and heterocyclic amines. In order to develop the new bacterial mutagenicity test system with human P450, a full length of human P450 1A2 cDNA inserted into pCW bacterial expression vector was introduced to Escherichia coli WP2 uvrA strain which is a well-known E. coli strain for bacterial reverse mutagenicity assay. Expressed human P450 1A2 showed typical P450 hemoprotein spectra. Maximum expression was achieved at 48 hrs after incubating at $30^{\circ}C$ in terrific broth containing ampicillin, IPTG and other supplements. High level expression of P450 1A2 in E. coli WP2 uvrA membranes was determined in SDS-PAGE. The well-known mutagens 2-aminoanthracene and MElQ increased the revertant colonies of E. coli WP2 uvrA expressing human P450 1A2 without an exogenous rat hepatic post-mitochondrial supernatant (S9 fraction) in a dose-dependent manner. The results show that the functional expression of human P450 in bacterial mutagenicity tester strain will provide a useful tool for studying the mechanism of the mutagenesis and carcinogenesis of new drugs and environmental chemicals.

• 한국축산식품학회지
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• 제37권6호
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• pp.799-803
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• 2017

In the present study, centrifugation and filtration pretreatments were evaluated to decrease sample preparation time and to improve the sensitivity and specificity of multiplex polymerase chain reaction (PCR) for the detection of low levels of pathogenic Escherichia coli in various foods. Pathogenic E. coli (E. coli NCCP11142, E. coli NCCP14037, E. coli NCCP 14038, E. coli NCCP14039, and E. coli NCCP15661) was inoculated into pork, beef, and baby leafy vegetables at 1, 2, and 3 Log CFU/g. The samples were shaken 30 times (control), then centrifuged or filtered. DNA extracts from the samples were subjected to PCR using the $Powerchek^{TM}$ Diarrheal E. coli 8-plex Detection Kit. In the pork samples, no E. coli was detected in the control samples, while E. coli were detected in 100% of 3-Log CFU/g inoculated and centrifuged samples, and in 100% of 2 and 3-Log CFU/g inoculated, and filtered samples. In the beef samples, all control samples appeared to be E. coli-negative, while E. coli was detected in 50-75% of centrifuged samples, regardless of inoculated level, and in 100% of 2 and 3-Log CFU/g inoculated, and filtered samples. In baby leafy vegetables, E. coli were not detected in 25-50% of the control samples, while E. coli were detected in 0-25% of the centrifuged samples, and 75-100% of the filtered samples, depending on the inoculum amount. In conclusion, filtration pretreatment can be used to minimize sample preparation time, and improve the sensitivity and specificity of rapid detection of pathogenic E. coli in various foods.

• 한국미생물·생명공학회지
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• 제48권1호
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• pp.24-31
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• 2020

Five genes (mxbDM, mxcQE and mxaB) are responsible for the transcription of methanol oxidation genes in Methylobacterium strains. Among these, MxbDM and MxcQE constitute the two-component system (TCS) regulating methanol metabolism. In this study, we integrated the methanol-sensing domain of MxbD and MxcQ with the EnvZ/OmpR from Escherichia coli. The domain-swapping strategy resulted in chimeric histidine kinases (HK's) MxbDZ and MxcQZ AM1 containing recombinant E. coli. Real-time quantitative PCR was used to monitor OmpC expression mediated by the chimeric HK and response regulator (RR) OmpR. Further, an ompC promoter based fluorescent biosensor for sensing methanol was developed. GFP fluorescence was studied both qualitatively and quantitatively in response to environmental methanol. GFP measurement also confirmed ompC expression. Maximum fluorescence was observed at 0.05% methanol and 0.01% methanol using MxbDZ and MxcQZ AM1, respectively. Thus the chimeric HK containing E. coli were found to be highly sensitive to methanol, resulting in a rapid response making them an ideal sensor.

• Fisheries and Aquatic Sciences
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• 제18권3호
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• pp.235-240
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• 2015

Seasonal variation in the prevalence of norovirus in oysters Crassostrea gigas was investigated and compared to levels of Escherichia coli, a fecal indicator in oysters. Oysters were collected from Iwon-myeon, Taean-gun, Korea, a primary production area for European Union export of oysters between 2013 and 2014. We observed seasonality in the prevalence of norovirus in oysters, with a higher prevalence and viral load detected during winter months. Oysters taken from production areas that complied with the European Union standard for raw consumption (< 230 MPN/100 g of E. coli) had 22.1% of the samples test positive for norovirus (15/68 samples). However, norovirus was not detected in any of the samples (0%, 0/4 samples) that were collected from production sites that exceeded the standard fecal contamination level for raw consumption (> 230 MPN/100 g of E. coli). These results indicated that there is a negative correlation between the prevalence of norovirus and high levels of E. coli in oysters. Therefore, our results suggest that current food safety guidelines using only a bacterial fecal contamination indicator, E. coli, may not adequately assess shellfish production areas for viral and bacterial contamination.

• 한국식품과학회지
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• 제29권5호
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• pp.1016-1020
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• 1997

본 연구는 Escherichia coli O157:H7 균주를 살균하고자 감마선 단독 및 가열과의 병용처리 효과를 조사하였다. E. coli O157:H7 균주의 가열 단독처리시 D값은 $50^{\circ}C$에서 129.2분, $55^{\circ}C$에서 27.1분, $60^{\circ}C$에서 2.4분으로 나타났다. E. coli O157:H7 균주는 0.03 M cysteine, 1% sodium citrate 및 5% sucrose가 첨가된 배지에서는 열에 대한 저항성이 증가하였고 1%, meat extract, 1% casein 및 1% casamino acid가 첨가된 배지에서는 감소하였다. 감마선 단독처리시는 $D_{10}$ 값과 불활성화 계수가 0.116 kGy와 $17{\sim}25$ 이였으나 가열과의 병용처리시는 약 0.07 kGy와 $25{\sim}41$로 나타났다. 이로서 가열과 방사선의 병용처리는 E. coli O157:H7 균주의 방사선 감수성을 현저하게 상승시켜 본 균주의 살균에 효과적이었다.