• Korean Journal of Microbiology
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• v.27 no.1
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• pp.16-20
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• 1989

The effect of E. coli plasmid DNA sequences contained by chimeric vectors on plasmid replication was investigated. We constructed YRp7- or 2.$\mu$m circle-based plasmids containing E. coli plasmid DNA sequences and those not containing it. By examining their maintenance in yeast, we showed that plasmid without E. coli plasmid DNA sdquences was nore stable and presented higher copy number, and espressed higher level of hepatitis B viral surface antigen as a foreign gene. This result suggested that E. coli plasmid DNA sequences within chimeric plasmid somehow inhibited plasmid replication in yeast.

• Journal of Microbiology and Biotechnology
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• v.4 no.1
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• pp.13-19
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• 1994

A model equation to describe the plasmid instability in recombinant Escherichia coli fermentation is proposed. The equation allows one to estimate easily the two model parameters; (1) the difference in the specific growth rates between plasmid-free cells and plasmid-harboring cells ($\delta$), and (2) the probability of plasmid loss by plasmid-harboring cells ($\rho$). The estimated values of $\delta and \rho$ were in the range of 0.02-0.07 and $10^{-3}-10^{-5}$, respectively, and were strongly dependent on the dilution rate. As another parameter, the ratio of specific growth rates of plasmid-free cells and plasmid-harboring cells ($\alha$) was calculated and the result showed the highest value of 1.28 at the lowest dilution rate of 0.075 $hr^{-l}$, examined in this work. By the sensitivity analyses on the estimates of $\delta and \rho$, it was found that the growth rate difference ($\delta$) affected the plasmid instability more seriously than the probability of plasmid loss ($\rho$). Furthermore, the profound instability of plasmid at low dilution rate could be explained by the high values of $\alpha and \rho$.

• Microbiology and Biotechnology Letters
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• v.17 no.1
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• pp.51-55
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• 1989

The conjugally transferred TOL plasmid or NAH plasmid was stably maintained and expressed in n-alkane assimilating Pseudomonas putida KCTC 2405. However, these plasmids were not able to coexist in this strain because of incompatibility. The incompatibility of TOL and NAH plasmid was bypassed using CAM::TOL* plasmid, which was constructed by the transposition of only tol gene without incompatibility system in TOL plasmid into CAM plasmid. p. putida 3SK capable of growing on m-toluate, naphthalene, camphor, and n-alkane(C8-C24) was constructed by the conjugal transfer of NAH plasmid into n-alkane assimilating p. putida SK carrying CAM:: TOL* plasmid. CAM::TOL＊ plasmid in p. putida 3SK was stable on the selective media but unstable on the nonselective media.

• KSBB Journal
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• v.15 no.1
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• pp.84-87
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• 2000

We studied the effect of ultrasoft X-ray obtained from the Pohang Light Source (PLS), on the mutation of E. coli and the damage of plasmid. After irradiation, the supercoiled plasmid DNA converted to the relaxed-form, and then to the linear-form. We transformed the irradiated plasmid DNA and isolated $\beta$-galactosidase mutants. We also isolated $\beta$-galactosidase mutants from the directly irradiated cells. There were preferred mutational sites on DNA induced by ultrasoft X-ray.

• Korean Journal of Veterinary Research
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• v.35 no.3
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• pp.537-542
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• 1995

In this study, we aim to find the presence of virulence-related plasmid in Salmonella isolates from poultry, and the difference between S pullorum and S gallinarum on the plasmid profile and antibiotics resistance. We used seventeen isolates of Salmonella spp that were isolated from poultry. Thirteen isolates, S typhimurium(ST), S pullorum(SP) and S gallinarum(SG), contained virulence-related plasmids. These are 95Kd plasmid in ST and 85Kd plasmid in SP and SG. Three(1/4 of ST, 1/1 of SE, and 1/9 of SP) isolates have no detectable plasmids. The isolates of ST have relatively variable plasmid profile but the isolates of S pullorum except No 12(additional 3.0Kb plasmid) have common 85K6, 8.1Kb, 4.0Kb and 2.3Kb plasmid and two of three isolates of S gallinarum have common 85Kb, 4.0Kb and 2.3Kb plasmid but the rest has only 85Kb plasmid. Interestingly, all of the isolates of SP have 8.1Kb plasmid, and same size of plasmid is also found in one of ST isolates. All of the isolates have the resistance to penicillin, chloramphenicol, rifampicin, streptomycin, sulfamethazine and some isolates show the resistance to ampicillin and tetracycline. There is no relatedness between plasmid profile and antibiotics resistance and no differences between SP and SG in antibiotics resistance. Therefore further differentiation of each isolates by restriction enzyme assay and, if possible, charaterization of each plasmid, especially, 8.1Kb plasmid in SP and ST, may be necessary.

• Korean Journal of Microbiology
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• v.24 no.2
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• pp.106-112
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• 1986

The large plasmid (about 180 megadaltons) was isolated from the aquatic strain of Pseudomonas which was found to degrade salicylate. It was found that the plasmid could be isolated under gentle conditions in comparison with other methods. The yield of covalently closed circular DNA was enganced by heat treatment at $55^{\circ}C$ after denaturing the chromosomal DNA with alkaline sodium dodecyl sulfate (pH 12.45), and the plasmid DNA was selectively concentrated by utilizing 10% polyethylene glycol as final concentration. It was also found that the cured strains with mitomycin C did not show any growth on the medium containing salicylat6e, therefore, it was concluded that the plasmid might play and important role on the salicylate degradation.

• Journal of Microbiology and Biotechnology
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• v.25 no.10
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• pp.1621-1628
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• 2015

Chlamydia possesses a conserved 7.5 kb plasmid that is known to play an important role in chlamydial pathogenesis, since some chlamydial organisms lacking the plasmid are attenuated. The chlamydial transformation system developed recently required the use of plasmid-free organisms. Thus, the generation and identification of plasmid-free organisms represent a key step in understanding chlamydial pathogenic mechanisms. A tricolor immunofluorescence assay for simultaneously detecting the plasmid-encoded Pgp3 and whole organisms plus DNA staining was used to screen C. muridarum organisms selected with novobiocin. PCR was used to detect the plasmid genes. Next-generation sequencing was then used to sequence the genomes of plasmid-free C. muridarum candidates and the parental C. muridarum Nigg strain. We generated five independent clones of plasmid-free C. muridarum organisms by using a combination of novobiocin treatment and screening plaque-purified clones with anti-Pgp3 antibody. The clones were confirmed to lack plasmid genes by PCR analysis. No GlgA protein or glycogen accumulation was detected in cells infected with the plasmid-free clones. More importantly, whole-genome sequencing characterization of the plasmid-free C. muridarum organism and the parental C. muridarum Nigg strain revealed no additional mutations other than loss of the plasmid in the plasmid-free C. muridarum organism. Thus, the Pgp3-based immunofluorescence assay has allowed us to identify authentic plasmid-free organisms that are useful for further investigating chlamydial pathogenic mechanisms.

• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.433-436
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• 1990

The TOL plasmid, pWWO, conjugally transferred from Pseudomonas putida mt-2 was dissociated into TOL* and TOL $\Delta$A in P. putidu PpGl carrying CAM plasmid. The TOL* was integrated into the CAM plasmid, and the resulting plasmid was designated as CAM::TOL*. The introduction of NAH plasmid, belonging to Inc P9 incompatibility group, into P. putida CSTBA carrying CAM::TOLt plasmid and TOL A plasmid did not affect m-toluate catabolism, but resulted in expelling the TOL $\Delta$ plasmid.

• Journal of Radiation Protection and Research
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• v.31 no.2
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• pp.65-68
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• 2006

In this study, the extent of plasmid DNA damage was observed according to concentration of BSH(Boron Sulfhydryl Hydride) and irradiation doses of neutron and ${\gamma}$-ray. The plasmid used was both pBR 322 (2870 bp) and ${\Phi}X174$ RF(5386 bp) DNA. Plasmid DNA damage by irradiation in the presence of BSH was analyzed by agarose gel electrophoresis. In the neutron experiment, DNA damage of both plasmid DNAs was increased according to increasing the concentration of BSH and neutron doses. But in the ${\gamma}$-ray experiment, there appeared no dose dependency as compared to the neutron experiment. The extent of the plasmid DNA damage in the presence of BSH was somewhat different according to irradiation by neutron or ${\gamma}$-ray.

• Korean Journal of Microbiology
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• v.32 no.3
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• pp.192-197
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• 1994

Pseudomonas fluorescens which is able to utilize malonate as a sole carbon source was found to contain a novel 60 kb plasmid, which encodes the genes for the proteins to assimilate malonate, including malonate decarboxylase and acetyl-CoA synthetase. The evidence is as follows: The Pseudomonas cured with mitomycin C was unable to grow on malonate-medium as well as it lost plasmid. The plasmid isolated from the Pseudomonas could be introduced into E. coli strain JM103 and DH1 by transformation. The transformed E. coli was able to grow on malonate-medium and could transmit its plasmid back to the cured P. fluorescens by conjugation. The existence of the plasmid in the transformed E. coli was confirmed by hybridization with a labeled probe prepared from 12 kb segment of the plasmid. Dot hybridization showed that the copy number of the plasmid in the transformed E. coli is at least 13 times higher than in the wild type P. fluorescens. The two key enzymes, malonate decarboxylase and acetyl-CoA synthetase, were inducible by malonate in the transformed E. coli.