• Food Science and Preservation
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• v.24 no.6
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• pp.778-785
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• 2017

This study was conducted to develop a predictive model for the growth of Escherichia coli strain RC-4-D isolated from red kohlrabi sprout seeds. We collected E. coli kinetic growth data during red kohlrabi seed sprouting under isothermal conditions (10, 15, 20, 25, and $30^{\circ}C$). Baranyi model was used as a primary order model for growth data. The maximum growth rate (${\mu}max$) and lag-phase duration (LPD) for each temperature (except for $10^{\circ}C$ LPD) were determined. Three kinds of secondary models (suboptimal Ratkowsky square-root, Huang model, and Arrhenius-type model) were compared to elucidate the influence of temperature on E. coli growth rate. The model performance measures for three secondary models showed that the suboptimal Huang square-root model was more suitable in the accuracy (1.223) and the suboptimal Ratkowsky square-root model was less in the bias (0.999), respectively. Among three secondary order model used in this study, the suboptimal Ratkowsky square-root model showed best fit for the secondary model for describing the effect of temperature. This model can be utilized to predict E. coli behavior in red kohlrabi sprout production and to conduct microbial risk assessments.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.680-683
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• 2000

A cytochrome c-552 from a thermophilic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus, was amplified using PCR. The cytochrome c-552 gene was cloned into E. coli vector pAlter-1 and transferred to JM109. Glutamine of cytochrome c-552 protein was changed to cysteine through point mutation.

• Archives of Pharmacal Research
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• v.21 no.2
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• pp.106-112
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• 1998

Structure-activity relationship of 20 fluoroquinolones was studied using the susceptible and 4 resistant Escherichia coli which were developed against 4 fluoroquinolones [ciprofloxacin (1), KR-10755 (6), norfloxacin (2), and ofloxacin (3)] in our laboratory. The C-7 and C-8 substituents of fluoroquinolone were important in various functions such as the inhibitory activity on DNA gyrase, permeability, and efflux. Among 20 fluoroquinolones, compounds with a 3-methyl-3,7-diazabicyclo[3.3.0]octan-1(5)-ene-7-yl substituent at the C-7 position or a chlorine substituent at the C-8 position showed a good inhibitory activity on DNA gyrase (especially a mutated DNA gyrase). Compounds with a 3,7-diazabicyclo [3.3.0]octan-1(5)-ene-7-yl substituent at the C-7 position showed good permeability in the susceptible and resistant strains, while compounds with a fluorine substituent at the C-8 position were less eff luxed from cells.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1711-1716
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• 2010

A gene encoding the ${\beta}$-xylosidase/${\alpha}$-arabinofuranosidase (XylC) of Paenibacillus woosongensis was cloned into Escherichia coli. This xylC gene consisted of 1,425 nucleotides, encoding a polypeptide of 474 amino acid residues. The deduced amino acid sequence exhibited an 80% similarity with those of both Clostridium stercorarium ${\beta}$-xylosidase/${\alpha}$-N-arabinosidase and Bacillus cellulosilyticus ${\alpha}$-arabinofuranosidase, belonging to the glycosyl hydrolase family 43. The structural gene was subcloned with a C-terminal His-tag into a pET23a(+) expression vector. The His-tagged XylC, purified from a cell-free extract of a recombinant E. coli BL21(DE3) Codon Plus carrying a xylC gene by affinity chromatography, was active on para-nitrophenyl-${\alpha}$-arabinofuranoside (pNPA) as well as para-nitrophenyl-${\beta}$-xylopyranoside (pNPX). However, the enzymatic activities for the substrates were somewhat incongruously influenced by reaction pHs and temperatures. The enzyme was also affected by various chemicals at different levels. SDS (5 mM) inhibited the enzymatic activity for pNPX, while enhancing the enzymatic activity for pNPA. Enzyme activity was also found to be inhibited by addition of pentose or hexose. The Michaelis constant and maximum velocity of the purified enzyme were determined for hydrolysis of pNPX and pNPA, respectively.

• Journal of Life Science
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• v.8 no.3
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• pp.263-271
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• 1998

One of the better-characterized transcription factor of E. coli is the cAMP receptor protein(CRP) and the CRP binds cAMP and DNA. The cAMP-CRP complex is involved in regulation of many genes at bacteria. The cAMP-CRP regulatory element represents, in some respects, a global regulatory network. The aim of this work was to study the structure and the mechanisms controlling the expression of CRP in Serratia marcescens. We have been get 5 different clones from Serratia which stimulated the cells to use maltose as a sole carbon source in E. coli TP2139. The crp gene clone, pCKB12, was confirmed by Southern hybridization with E. coli crp gene. The location of the crp gene was determined by construction subclones carrying various portions of pCKB12. To investigate the potential role of CRP in E. coli, lacZ fused plasmids were constructed and investigated the ${\beta}$-galactosidase activity of the fused plasmid. The Serratiamarcescens cAMP receptor protein can substitute the E. coli CRP in transcriptional activation at the lacZ gene. These results suggest that Serratia marcescens cAMP receptor protein complex functions to regulate several promoters in E. coli.

• Microbiology and Biotechnology Letters
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• v.48 no.1
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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.

• Journal of Microbiology and Biotechnology
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• v.6 no.6
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• pp.451-455
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• 1996

Physiological studies on the expression of Bacillus thuringiensis subsp. tenebrionis (Btt) gene coding for insecticidal protein in recombinant Escherichia coli 537 were carried out to identify optimal culture condition. It was necessary to shift culture temperature from 30 to $42^{\circ}C$ to express the gene. Expression of the Btt toxin gene by recombinant E. coli 537 began within one hour after induction. Complex nitrogen sources increased production of the insecticidal protein. The total insecticidal protein was 0.5 g/I when using yeast extract as a complex nitrogen source. Soybean hydrolysate showed apparently the highest induction efficiency. After induction, the cellular content of the insecticidal protein was 5.4 times higher than it had been before induction. The optimal cultivation strategy was found to grow cells for 7hours at $30^{\circ}C$ and then 5-8 hours at $42^{\circ}C$. The optimal cultivation pH for the production of insecticidal protein was 6.5. The Btt toxin produced by the recombinant E. coli 537 was found to have the same level of potency against Colorado potato beetle as the original toxin.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.635-638
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• 2004

An ATP-binding-cassette (ABC) transporter gene in the cephabacin biosynthetic gene cluster of Lysobacter lactamgenus was characterized. The amplified orf10 (cpbJ) gene was subcloned into pET-28a(+) vector and expressed in E. coli BL21(DE3) strain by 0.5 mM IPTG at $30^{\circ}C$. The membrane fraction of recombinant E. coli cells was separated by ultracentrifugation, and solubilized using 2.5% octyl-$\beta$-D-glucoside. Using the solubilized membrane fraction, the artificial proteoliposomes were reconstituted and analyzed for the biological activity of CpbJ protein. Upon measuring ATPase activity, the proteoliposome made from recombinant E. coli membrane proteins showed slightly higher activity than that from host E. coli membrane proteins. In the measurement of membrane transport activity, the reconstituted proteoliposome of recombinant E. coli membrane proteins exhibited higher activity when both substrates of cephalosporin C and L-Ala-L-Ser were applied, compared to the case of cephalosporin C or L-Ala-L-Ser only. It implies that the CpbJ protein is an ABC transporter secreting cephabacin antibiotics synthesized in cytoplasm.

• Journal of Microbiology and Biotechnology
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• v.5 no.1
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• pp.14-17
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• 1995

Endoglucanase gene of Pseudomonas sp. LBC505 was previously cloned in pUC19 to yield plasmid pLCl. The Pseudomonas sp. LBC505 endoglucanase gene was subcloned in a temperature-regulated Es-cherichia coli expression vector, pAS1, containing the leftward promoter $P_L$ of bacteriophage lambda. The level of gene expression was controlled by the thermal inactivation of the heat-sensitive lambda cI857 repressor. Best yield of endoglucanase was obtained by lowering the incubation temperature to $37^{\circ}C$ after induction at $42^{\circ}C$ for 1h. Under these conditions enzyme production continued for about 5h at a gradually decreasing rate. Ecoli harboring recombinant plasmid pASC10 expressed 4.3 times as much CMCase activity as E.coli containing pLCl. To enhance the expression level of endogl, ucanase gene, we have also changed the presumptive Shine-Dalgamo sequence (AGAGGT) of the gene to consensus sequence (AGGAGGT) by site-directed mutagenesis. The genes mutated were subcloned in pASl resulting in the formation of recombinant plasmid pASS50. E.coli harboring the plasmid pASS50 expressed 6.2-fold higher levels of CMCase activity than that of E.coli harboring pLC1.

• Korean Journal of Veterinary Research
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• v.55 no.4
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• pp.259-262
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• 2015

The antibacterial effects of a combination of Coptidis rhizoma and Galla rhois extracts (CGE) were evaluated in piglets. The minimum bactericidal concentration of CGE was 2.0 mg/mL. Thirty 5-week-old piglets were challenged with Campylobacter (C.) coli after allocation to three different groups, a control and two treatment groups fed with CGE at 2.0 or 4.0 g/kg feed for 7 days. On day 7, C. coli in the feces of the CGE-treated groups were significantly lower than in the control (p < 0.01). These results suggest that CGE can be used to control C. coli in piglets.