• Environmental Mutagens and Carcinogens
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• v.9 no.2
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• pp.111-121
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• 1989

Ps. aeruginosa 의 DNA repair 기구 결손변이주인 rec-, Hcr- 그리고 R931 plasmid 를 가진 R2 (Carbenicillin, Kanamycin, Streptomycin) plasmid transconjugants 가 R2 Plasmid 획득에 의해서 Gamma선 및 돌연변이제 (4NQO, NTG)에 대해서도 내성을 증강시키는지를 검토함으로써 방사선에 대한 내성화 기구를 해명하고자 했다. 그리고, DNA repair 기구에 작용하는 DNA polymerase I 생산에 관여하는 유전자가 R2 plasmid에 code 되어 있는지를 검토하여 다음과 같은 결과를 얻었다. 1) Ps. aeruginosa PAO균주의 R2 plasmid transconjugants는 R2 plasmid 획득에 의해 자외선, Gamma선 및 돌연변이제에 대한 내성을 부여받았으나 transconjugant 균주에 따라 다른 종류의 내성결과를 얻어졌다.

• Korean Journal of Microbiology
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• v.20 no.1
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• pp.11-20
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• 1982

A study was undertaken to examine the effect of curing agents on the stability, curing and segregation of R plasmid pSL100. And also the stability, transfer frequency, and recombination of its segregants obtained from curing agent treatment were studied. Ethidium bromide, acridine orange, and mitomycin-C were used as curing agent. The results obtained were as follows ; 1. The curing agent ethidium bromide, acridine orange, and mitomycin-C were not effective for curing the multiple antibiotic resistant determinant of pSL100 in Salmonella typhimurium and Escherichia coli. However, they induced plasmid segregation with high frequency in S.typhimuruim LT-2strains. TcApSmCm, TcSmCmKm, TcApCm, TcAp, TcKm, Tc segregants were obtained. 2. The resistant markers of the segregents were transferred to S.typhimurium LT-2 strains with high frequencies whereas they were transferred to E.coli K-12 only with low frequencies. 3. The transconjugants obtained from conjugation between two different S.typhimurium segregants were similar to the phenotype of the original R factor pSL100 and the resistant markers were transferred to the S.typhimurium LT-2 or E.coli strain with equal frequencies, indicating that they are recombinants. 4. The transconjugants obtained from conjugation between pSL100 segrgants and pKM101, or pBR322 possessed the resistant markers of the two parental plasmids and they were transferred to both S.typhimurium and E.coli K-12 strains with the same frequencies and maintained stably, suggesting that they are also recombinants. 5. The recombinant pSL100 could be also obtained in rec A-strains of E.coli, suggesting that the gene function of rec A is required for the recombination of pSL100 segregants in E.coli.

• Journal of Microbiology and Biotechnology
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• v.4 no.3
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• pp.165-170
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• 1994

An efficient and convenient method of introducing transposable elements into acetic acid bacteria was developed by the method of conjugal transfer. The ampicillin-resistant strain, Acetobacter sp. HA, was selected to be conjugated with two E. coli strains, WA803 containing pGS9 and AC8001 harboring pJB4JI. The Tn5 containing suicide vector pGS9 or pJB4JI, was transferred from E. coli to Acetobacter sp. HA and kanamycin-ampicillin-resistant transconjugants obtained at high frequencies. The conjugal frequencies of pGS9 and pJB4JI were 6.20$\times$$l0^{-1} and 2.79$\times$l0{-1}$ per recipient, respectively. The transfer method was applied on four different strains of Acetobacter. The conjugal transfer frequencies ranged from 2.00$\times$$l0^{-2} to 4.45$\times$l0^{-8}$ per recipient in the three strains. Some transconjugants tested were found to contain Tn5 DNA in their genomes and this was confirmed by Southem blot analysis. This is the first study which shows that Tn5 mutagenesis can be applied to successfully isolate mutants of Acetobacter genus.

• Korean journal of applied entomology
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• v.32 no.3
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• pp.330-337
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• 1993

A bacterium, pathogenic to Nilaparvata lugens Stal. causing high mortality in 3~5 days, were selected and identified as Serratuz marcescens biotype A2a which is not a nosocomlally infective strain. In order to determine the characters of Serratia marcesce'1lS associated with insect pathogenicity, Tn5 mutagenesis was carried out by conjugating with E. coli pJB4J1. Transconjugants were plate-assayed for missing chitinase, protease and DNase activity. A protease negative mutant was selected for missing JOseet pathogenicity. SEM and TEM revealed the presence of bacterial cells in the epithelial tissue of inner abdomal tissue of the hypodermic layer of abdomen. Such a colonization was limmited to the subjacent tissue inside the intacL cuticular epidermis. These observation supported our result of pathogenicity tests of transconjugants.

• The Journal of the Korean Society for Microbiology
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• v.21 no.1
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• pp.17-31
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• 1986

Forty clinical isolates of Serratia marcescens were tested for their susceptibility to 19 antimicrobial drugs and studied on the molecular characteristics of R plasmids. Cefotaxime (Ct) was the most effective drug and only 2 (5%) strains were resistant to this drug. Thirteen to 18% of strains were resistant to cefoperazone (Cz), amikacin (Ak). and trimethoprim (Tp), and 28 to 40% were resistant to piperacillin (Pi), nalidixic acid (Na), gentamicin (Gm), and cefoxitin (Cx). A majority of strains were resistant to carbenicillin (Cb), tobramycin (Tp), kanamycin (Km), and cefamandole (Cd), and all to cephalothin. One half of the isolates were resistant to 10 or more drugs. $MIC_{90}$ of Pi to Gm-resistant strains (Gm') were 8 times higher than that to Gm-susceptible strains (Gm'), but $MIC_{90}$ of Ak, Cx, Ct, and Cz were almost the same between both Gm' and Gm' strains. Nine (23.7%) strains among 38 of multiply drug-resistant S. marcescens transferred conjugally their partial patterns of resistance to E. coli or Klebsiella strains, and two S. marcescens strains producing bacteriocin transferred their resistance to Klebsiella only, but not to E. coli. The plasmid profiles of S. marcescens were studied by the methods of SDS lysis and agarose gel electrophoresis. Twenty-four (60%) strains carried one to four plasmids of 1.4. to 144 Mdal, and conjugative R plasmids of 49 to 127 Mdal were noted in transconjugants. MIC levels of drugs in transconjugants were variable by the R plasmids and recipient strains.

• Korean Journal of Veterinary Service
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• v.42 no.1
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• pp.17-24
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• 2019

The aim of this study was to investigate the prevalence and characterization of plasmid-mediated quinolone resistance (PMQR) gene in 79 Enterobacteriaceae isolated from dogs and cats. Of 79 isolates, PMQR genes were found in 10 (12.7%) isolates, including aac(6')-lb-cr, qnrB, qnrS and qnrA detected alone or in combination in 8 (10.1%), 4 (5.1%), 2 (2.5%) and 1 (1.3%) isolates, respectively. Interestingly, two qnrS genes were detected in nalidixic acid and ciprofloxacin susceptible isolates. Extended-spectrum ${\beta}$-lactamase (ESBL) was detected in 90% (9 isolates) of PMQR positives isolates. Among ESBL genes, CTX-M, TEM and SHV were detected in 9, 8 and 3 isolates, respectively. Almost all PMQR genes were detected in co-existence with ESBL genes. All PMQR positives isolates were multidrug resistance (i.e. resistant to five or more antibiotics). qepA, OXA and CMY-2 genes were not found. The six transconjugants were obtained by conjugation experiment. The aac(6')-lb-cr, qnrB and qnrS were co-transferred with CTX-M, TEM and/or SHV, whereas qnrA was not observed among transconugants. This is the first report of the presence of aac(6')-lb-cr and qnrA gene among Enterobacteriaceae isolates from dogs in Korea. The prudent use of antimicrobials and continuous monitoring for companion animals are required.

• Journal of Microbiology and Biotechnology
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• v.30 no.8
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• pp.1180-1183
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• 2020

The prevalence and characterization of plasmid-mediated quinolone resistance (PMQR) determinants in ciprofloxacin-resistant Escherichia coli isolated from a Korean commercial layer farm were studied. A total of 45 ciprofloxacin-resistant E. coli isolates were recovered and all isolates were multidrug-resistant. Eight isolates have the PMQR genes aac(6')-Ib-cr, qnrS1, and qnrB4, and seven isolates exhibited double amino acid exchange at both gyrA and parC, and have high fluoroquinolone minimum inhibitory concentrations. Five transconjugants demonstrated transferability of PMQR and β-lactamase genes and similar antimicrobial resistance. Because PMQR genes in isolates from commercial layer chickens could enter the food supply and directly affect humans, control of ciprofloxacin resistance is needed.

• Journal of Microbiology and Biotechnology
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• v.2 no.2
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• pp.115-121
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• 1992

In order to broaden the spectrum of substrate utilization of a Gram negative bacterium Zymomonas mobilis which has a great potential as an industrial ethanol producing microorganism, cloning of $\alpha$-amylase gene into Z. mobilis ZM4 was tried. The $\alpha$-amylase gene was isolated from Bacillus stearothermophilus. By Southern blot analysis, it was proven that the $\alpha$-amylase gene fragment was originated from a naturally occuring plasmid of B. stearothermophilus ATCC 31195. To place $\alpha$-amylase gene under the control of Z. mobilis promoter, two different Z. mobilis expression vectors, pZA26 and pLOI204, were used. The truncated $\alpha$-amylase gene was then introduced into these vectors. Both qualitative and quantitative activities of $\alpha$-amylase were observed in Z. mobilis cells harboring these plasmids with the $\alpha$-amylase gene inserted. Gas chromatographic analysis of ethanol showed that one of the Z. mobilis transconjugants was capable of producing 67 mM ethanol from rich medium(RM) containing 5% soluble starch as a sole carbon source.

• Microbiology and Biotechnology Letters
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• v.19 no.1
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• pp.25-30
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• 1991

The crystal protein gene (cp) of Bacillus tizuringienszs subsp. liuvstaki (B.t.k.) HI173 was subcloned into HanzHI site of central region (Tn5-cp) or BglII site of IS50L region (IS50L-cp) in Tn5, and transposed into the chromosomal DNA of five strains of root-colonizing Pseudomonas. The expression of cp gene in Acwiomoncrs transconjugants was demonstrated by immunoblot analysis and bioassay against larvae of the Hyphantria cunea.

• Journal of Microbiology and Biotechnology
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• v.14 no.1
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• pp.56-61
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• 2004

A plasmid pSDK-l containing the Escherichia coli phosphofructokinase-l gene (pfkA) was constructed, and transferred into extremely acidophilic Acidithiobacillus thiooxidans Tt-7 by conjugation with the aid of plasmid RP4 at a frequency of $10^{-5}$ per recipient. This plasmid was stable in A. thiooxidans. The pfkA gene from E. coli could be expressed in this obligately autotrophic bacterium, but the enzyme activity (21.6 U/g protein) was lower than that in E. coli (K12: 85.9 Dig protein; DF1010 carrying plasmid pSDK-l: 96.6 U/g protein). In the presence of glucose, the Tt-7 transconjugants consumed glucose, leading to a better growth yield.