• Korean Journal of Microbiology
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• v.28 no.2
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• pp.169-173
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• 1990

For the overproduction of L-phenylalanine using Escherichia coli, the authors constructed various recombinant plasmids including pMW 10, pMW 11 and pMW 12. The $aroF{FR}$ and $pheA^{FR}$ genes for the production of L-phenylalanine were isolated from Escherichia coli MWEC 101-5 strains. The productivity and atability of Escherichia coli regulatory mutants containing recombinant plasmids were investigated to evaluate the efficiency of the $aroF^{FR}$ and $pheA^{FR}$ genes. The MWEC 101-5/pMW 11 strain produced 24.3g/l of L-phenylalanine while its stability was 73.8 percent. The specific activity of prephenate dehydratase in the MWEC 101-5/pMW 11 strain increased by 26-fold compared with that of Escherichia coli K-12.

• BMB Reports
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• v.38 no.1
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• pp.89-96
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• 2005

Earlier, we reported that the bacteriophage $\lambda$ P gene product is lethal to Escherichia coli, and the E. coli rpl mutants are resistant to this $\lambda$ P gene-mediated lethality. In this paper, we show that under the $\lambda$ P gene-mediated lethal condition, the host DNA synthesis is inhibited at the initiation step. The rpl8 mutation maps around the 83 min position in the E. coli chromosome and is 94% linked with the dnaA gene. The rpl8 mutant gene has been cloned in a plasmid. This plasmid clone can protect the wild-type E. coli from $\lambda$ P gene-mediated killing and complements E. coli dnaAts46 at $42^{\circ}C$. Also, starting with the wild-type dnaA gene in a plasmid, the rpl-like mutations have been isolated by in vitro mutagenesis. DNA sequencing data show that each of the rpl8, rpl12 and rpl14 mutations has changed a single base in the dnaA gene, which translates into the amino acid changes N313T, Y200N, and S246T respectively within the DnaA protein. These results have led us to conclude that the rpl mutations, which make E. coli resistant to $\lambda$ P gene-mediated host lethality, are located within the DNA initiator gene dnaA of the host.

• Childhood Kidney Diseases
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• v.10 no.2
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• pp.192-200
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• 2006

Purpose : This study was performed to identify longitudinal changes in the prevalence of organisms isolated from urinary tract infection(UTI) and in the pattern of Escherichia coli susceptibility to antibiotics during the past 10 years in children with UTI. Methods : We performed a retrospective study of a total of 192 urine cultures from children with UTI in the Department of Pediatrics, Seoul Adventist Hospital over two periods(1st: 1995-2000, 2nd:2001-2005). Antimicrobial susceptibility of the isolates was compared between the two groups. Results : The pathogens of UTI in the two groups were similar. In the first period, E. coli was the leading uropathogen(66.2%) followed by Klebsiella pneumoniae(7.8%), Enterobacter cloacae(6.5%), and others(19.5%). In the second period, E. coli was the leading uropathogen(67%) followed by K. pneumoniae(12.2%), E. cloacae(3.5%), Enterobacter aerogenes(3.5%), and others(13.8%). The susceptibility pattern of E. coli to amoxicillin/clavulanate(87.5%, 81.0%) did not present any statistically significant difference between the two periods(P>0.05). The susceptibility of E. coli to TMP/SMX(52.4%, 50.0%) was still low with no significant difference between the two periods(P>0.05). Conclusion : Our results suggest that the use of amoxicillin/clavulanate is still an excellent therapeutic option in children with UTI. The low rate of susceptibility to TMP/SMX against uropathogens suggest that TMP/SMX may be reevaluated as the first-line therapeutic drug for UTI.

• Journal of Sensor Science and Technology
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• v.17 no.3
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• pp.195-202
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• 2008

A biosensor based on the measurement of capacitance changes has been designed and fabricated for simple and realtime detection of bacteria. Compared to an impedance measurement technique, the capacitance measurement can make additional measurement circuits simpler, which improves a compatability for integration between the sensor and circuit. The fabricated sensor was characterized by detecting Escherichia coli(E. coli). The capacitance changes measured by the sensor were proportional to E. coli cell density, and the proposed sensor could detect $1{\times}10^6$ cfu/ml E. coli at least. The real-time detection was verified by measuring the capacitance every 20 minutes. After 7 hours of E. coli growth experiment, the capacitance of the sensor in the micro volume well with $4.5{\times}10^5$ cfu/ml of initial E. coli density increased by 20 pF, and that in another wells with $1.5{\times}10^6$ cfu/ml and $8.5{\times}10^7$ cfu/ml initial E. coli density increased by 56 pF and 71 pF, respectively. The proposed sensor has a possibility of the real-time detection for bacterial growth, and can detect E. coli cells with $1.8{\times}10^5$ cfu in nutrient broth in 5 hours.

• Journal of Microbiology and Biotechnology
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• v.21 no.2
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• pp.204-211
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• 2011

To yield high concentrations of protein expressed by genetically modified Escherichia coli, it is important that the bacterial strains are cultivated to high cell density in industrial bioprocesses. Since the expressed target protein is mostly accumulated inside the E. coli cells, the cellular product formation can be directly correlated to the bacterial biomass concentration. The typical way to determine this concentration is to sample offline. Such manual sampling, however, wastes time and is not efficient for acquiring direct feedback to control a fedbatch fermentation. An E. coli K12-derived strain was cultivated to high cell density in a pressurized stirred bioreactor on a pilot scale, by detecting biomass concentration online using a capacitance probe. This E. coli strain was grown in pure minimal medium using two carbon sources (glucose and glycerol). By applying exponential feeding profiles corresponding to a constant specific growth rate, the E. coli culture grew under carbon-limited conditions to minimize overflow metabolites. A high linearity was found between capacitance and biomass concentration, whereby up to 85 g/L dry cell weight was measured. To validate the viability of the culture, the oxygen transfer rate (OTR) was determined online, yielding maximum values of 0.69 mol/l/h and 0.98mol/l/h by using glucose and glycerol as carbon sources, respectively. Consequently, online monitoring of biomass using a capacitance probe provides direct and fast information about the viable E. coli biomass generated under aerobic fermentation conditions at elevated headspace pressures.

• Journal of Microbiology and Biotechnology
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• v.29 no.12
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• pp.1975-1981
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• 2019

Recently, outbreaks of food-borne diseases linked to fresh produce have been an emerging public health concern worldwide. Previous research has shown that when human pathogens co-exist with plant pathogens, they have improved growth and survival rates. In this study, we have assessed whether Escherichia coli O157:H7 benefits from the existence of a phytopathogenic bacterium and the underlying mechanisms were further investigated. When Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) and E. coli O157:H7 were co-inoculated by either dipping or infiltration methods, the populations of E. coli O157:H7 increased; however, no effect was observed when type three secretion system (T3SS) mutants were used instead, suggesting that E. coli O157:H7 benefits from the presence of Pst DC3000. In addition, this study confirmed that the E. coli O157:H7 populations increased when they occupied the tomato leaf intercellular space; this colonization of the interior of the leaves was possible due to the suppression of the PAMP-triggered immunity (PTI) by Pst DC3000, in particular with the AvrPto effector. In conclusion, our data support a plausible model that E. coli O157:H7 benefits from the presence of Pst DC3000 via AvrPto suppression of the PTI resistance.

• Journal of Food Hygiene and Safety
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• v.14 no.4
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• pp.327-332
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• 1999

The prevalence and serotype of food-borne pathogens was investigated from 888 samples of chilled meat, 222 samples of packed frozen meat and 117 samples of imported frozen meat during the period from March 1996 to October 1998. Isolation rates of pathogens associated with food poisoning were revealed in order of Staphyloccus aureus, Campylobacter jejuni /coli, Listeria monocytogenes and Salmonella spp, but Escherichia coli O157:H7 was not isolated in all of the meat samples. Amusingly, Campylobacter jejuni /coli were isolated highly in refrigerated meat, but was not isolated in packed frozen meat. L. monocytogenes was encounted higher isolation frequency in packed frozen chicken meat than in refrigerated chicken meat. In the distribution of serotypes of isolates, most isolates of Sta. aureus classified as enterotoxin type C and D. All of the Salmonella spp. isolated from pork were diagnosed group A and most of isolates from chicken meat were grouped B and D. Most of L. monocytogenes isolated from chicken meat were grouped type 1 and a few number of isolates classified as type 4.

• Microbiology and Biotechnology Letters
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• v.34 no.1
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• pp.35-39
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• 2006

One of the fermentative metabolism of enteric Escherichia coli was imitated after rumen bacteria, which have high C4 metabolism. E. coli expresses phosphenolpyruvate carboxylase (PPC) for the pathway between phosphoenolpyruvate (PEP) and oxaloacetate (OAA) during glycolytic condition while expresses phosphoenolpyruvate carboxykinase (PCK) during gluconeogenic condition. In contrast to enteric E. coli, rumen bacteria express the PEP-OAA pathway only by PCK. To verify the effect of the regulation imitation on the C4 metabolism of E. coli, PPC-deficient E. coli strain with PCK expression in glycolytic condition was constructed. The PEP-OAA regulation modified E. coli strain increased 2.5-folds higher C4 metabolite than the wild type strain. The potential use of C4 metabolism by regulation control is discussed.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.552-559
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• 2003

The FimH subunit of type 1-fimbriated Escherichiu coli (E. coli) has been determined as a major cause for urinary tract infections. Thus, to produce a possible vaccine antigen against urinary tract infections, the fimIH gene was genetically coupled to the ctxa2b gene and cloned into a pMAL-p2E expression vector. The chimeric construction of pMALfimH/ctxa2b was then transformed into E. coli K-12 TB1 and its nucleotide sequence was verified. A fusion protein, based on fusing adhesin to the cholera toxin subunit A2B (CTXA2B), was induced with 0.01 mM isopropyl-${\beta}-D-thiogalactoside$ (IPTG) for 4 h at $37^{\circ}C$ to yield a soluble fusion protein. The fusion protein was then purified by affinity chromatography. The expressed fusion protein was confirmed by SDS-PAGE and Western blotting using antibodies to the maltose binding protein (MBP) or the cholera toxin subunit B (CTXB), plus the N-terminal amino acid sequence was also analyzed. The orderly-assembled fusion protein was confirmed by a modified $G_{Ml}-ganglioside$ ELISA, using antibodies to adhesin. The results indicated that the purified fusion protein was an adhesin/CTXA2B protein containing E. coli adhesin and the $G_{Ml}-ganglioside$ binding activity of CTXB. Accordingly, this adhesin/CTXA2B protein may be a potential antigen for oral immunization against uropathogenic E. coli.

• Journal of Microbiology and Biotechnology
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• v.17 no.6
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• pp.1045-1048
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• 2007

Two genes, dps encoding decaprenyl diphosphate synthase and dxs encoding 1-deoxy-D-xylulose 5-phosphate synthase, were isolated from Rhizobium radiobacter ATCC 4718. DNA sequencing analysis of the dps and dxs genes revealed an open reading frame of 1,077 bp and 1,920 bp, respectively. The heterologous expression in Escherichia coli BL21(DE3) was carried out in order to identify their functions. Recombinant E. coli BL21(DE3) harboring the dps gene produced $CoQ_{10}$ as well as $CoQ_8$ and $CoQ_9$, whereas E. coli harboring only the dxs gene produced more $CoQ_8$ compared with the wild-type E. coli. Additionally, the coexpression of dps and dxs genes in E. coli was carried out. The recombinant E. coli harboring only the dps gene produced $0.21{\pm}0.04\;mg/l$ of $CoQ_{10}$, whereas the coexpressed E. coli with dps and dxs genes produced $0.37{\pm}0.07\;mg/l$ of $CoQ_{10}$. HPLC analysis also showed that the $CoQ_{10}$ fraction (100% of the total CoQs distribution) was increased from $15.86{\pm}0.66%$ (only dps) to $29.78{\pm}1.80%$ (dps and dxs).