• Microbiology and Biotechnology Letters
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• v.13 no.3
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• pp.199-201
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• 1985

Plasmids, YEp13 and pMA56, were encapsulated Into liposomes by two different procedures during which the plasmid DNAs were exposed ether to 6$0^{\circ}C$ for 1.5 hr or to sonication for 2-5 min at 4$^{\circ}C$. The encapsulated plasmids were then reextracted and their physical conformations and transformation abilities were examined. It was confirmed from the results that both plasmid DNAs were remained stable throughout the procedures of encapsulation into 1iposomes.

• KSBB Journal
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• v.6 no.4
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• pp.385-388
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• 1991

Embryogenic cell suspension cultures of B. striata were established as transferred selected embryogenic callus into liquid medium. Protoplasts isolated from embryogenic cell suspensions were electroporated in buffered solutions containing plasmid DNA of pBI121. Transient GUS (beta-glucuronidase) activity measurement and selection for kanamycin resistent showed that expression of foreign genes and stable transformation were achieved. GUS transient gene expression was increased by increasing DNA concentration of pBI121 plasmid and affected by the level of the applied voltage. An optimal level of GUS activity was obtained after electroporation with a pulse of 200-300 voltage/1180 uF. Protoplast viability was up to the 80% at the optimal voltage.

• Korean Journal of Veterinary Research
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• v.28 no.1
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• pp.59-65
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• 1988

This paper deals with the 0 groups of citrate utilizing variants of Escherichia coli ($Cit^+$ E. coli) isolated from cattle, the production of colicin, hemolysin, K99 antigen, heat stable enterotoxin, and the isolation of plasmid DNA. Among 42 $Cit^+$ E. coli, 12 strains were 020, 9 strains 08, 5 strains 045, 3 strains 0115, 1 strain 064, 1 strain 0139 and remaining strains(11) were untypable. Thirty-nine(81.3%) out of 48 $Cit^+$ E. coli were produced colicin and 13(27.0%) were produced hemolysin. Of 12 $Cit^+$ E. coli bearing K99 antigen, 6(50.0%) were produced heat stable enterotoxin. In gel electrophoresis for the isolation of plasmid DNA, the number of plasmids varied from 1 to 7 in 10 $Cit^+$ E. coli. It's molecular weight ranged from 2 to 50 Mdalton, and 50 Mdalton plasmid was commonly existed in all strains.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.575-582
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• 1991

To increase the production of glutathione by the expression of recombinant gsh plasmids, two genes responsible for the biosynthesis of glutathione were isolated and cloned. To clone a gshI gene, the GS903 mutant strain, which is deficient in $\gamma$-glutamylcysteine synthetase activity, has been raised. A gshI gene was cloned using pBR322 plasmid as a 3.6 Kb PstI DNA fragment isolated from E. coli K-12 chromosomal DNA. Also a gshIl gene was cloned using pUC13 plasmid as a 2.2 Kb PstI-BamHI DNA fragment. To study the effects of plasmid copy number and passenger DNA size on the expression levels of the gsh genes, various recombinant plasmids containing different sets of genes were constructed. The expression levels of the gsh genes were increased approximately twice higher in pUC series plasmids than that in pBR322 plasmid. But the sizes of the passenger DNA containing the gsh genes in the vector plasmid did not affect on the expression levels of the gsh genes.

• Current Research on Agriculture and Life Sciences
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• v.12
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• pp.69-82
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• 1994

This study was conducted to investigate the physiological characteristics and to isolate plasmid DNA of R. japonicum strains. The results obtained were as follows; Strains S117, S118, 005, 011 and DY-1 were slow-growers and showed alkaline reaction, whereas strains S110, S111, S114, S116, S120 and 010 were fast-growers and produced acid reaction in YEM broth. All the fast- and slow-growing R. japonicum showed gram negative and formed mucous white colony on agar plate. After 7 days, the colonies of the fast-growers were between 2.0 and 4.0mm in diameter, whereas those of slow-growers were approximately between 0.5 and 1.5mm. The fast-growers were uniformly sensitive to the pH of 4.5 and tolerant of the pH of 9.5, whereas the reverse was found for the slow-growers. All the fast-growers were able to grow in the presence of 2% NaCl however the slow-growers were not grown. All the microorganisms grew rapidly in simple mineral salt medium containing as the sole source of carbon. Starch was rarely utilized. All the fast-growers utilized sucrose. The slow-growing R. japonicum strains examined usually contained 1 to 3 plasmid DNA ranging between 15Kb and 250 Kb, whereas the fast-growing R. japonicum strains contained 1 to 3 plasmid DNA ranging from 20 Kb to 250Kb.

• Journal of the Korean Society of Food Science and Nutrition
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• v.19 no.6
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• pp.565-570
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• 1990

The role of the active oxygens on plasmid DNA damage by carbonyl compounds derived from Maillard reaction was investigated. Plasmid DNA extracted from E. coli Hb1O1 was reacted with carbonyl compounds, such as glyoxal, methyl glyoxal, dihydroxyacetone, diacetyl, glyceraldehyde, glycolaldehyde and furfural with and without the active oxygen scavengers at 37$^{\circ}C$ for 6 hours, and then the degree of damage was determined by using 1 ％ agarose gel electro-phoresis. All of the carbonyl compounds except furfural caused to damage of DNA. Among these, glyoxal, methyl glyoxal and dihydroxyacetone markedly induced the damage of DNA. On the other hand, the DNA damage by the carbonyl compounds was greatly inhibited by catalase, superoxide dismutase and $\alpha$-tocopherol it is considered that the damage of DNA is due to active oxygens, such as singlet oxygen, hydrogen peroxide and superoxide anion generated during the autoxidation of carbonyl compounds.

• Microbiology and Biotechnology Letters
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• v.14 no.2
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• pp.155-160
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• 1986

$\alpha$-Amylase gene of B. amyloliquefaciens was cloned to E. coli-yeast shuttle vector YEp-13 and expressed in E. coli. Chromosomal DNA of B. amyloliquefaciens was partially digested with Sau3Al and YEp13 plasmid was cleaved with BamH1. The hybrid plasmid, pHA28, was constructed by shotgun method and transformed to E. coli C600 and HB101. The amount of $\alpha$-amylase produced by transformants of E. coli was about 20% to 30% of that produced by B. amyloli-quefaciens. About 65% of $\alpha$-amylase produced by transformant was secreted into periplasm and the others were located in cytoplasm. $\alpha$-Amylase production was maximal when transformants were cultivated for 15hr to 20hr. As the result of agarose gel electrophoresis, pHA28 plasmid was found to be various in its size. This result suggested that pHA28 plasmid was segregated.

• Microbiology and Biotechnology Letters
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• v.23 no.2
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• pp.164-169
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• 1995

An endogenous cryptic plasmid, pBL1, which has been used to construct plasmid vectors for coryneform bacteria producing amino acids, was eliminated from Brevibacterium lactofermentum. The pBL1 was partially digested with Sau3AI and the resulting DNA fragments were subcloned into a suicide vector pEM1 which contains a kanamycin-resistant (km$^{r}$) gene. KM$^{r}$ B. lactofermentum transconjugants were obtained by conjugal transfer of the pEM1 derivatives containing pBL1 DNA fragments from Escherichia coli into B. lactofermentum. A km$^{r}$ transconjugant was analyzed to contain a plasmid pEB14, which occurred in vivo by homologous recombination between pBL1 and the conjugal-transferred plasmid. The pEB14 including the pEM1-derived km$^{r}$ gene was found to be lost concomitantly with km$^{r}$ phenotype, resulting in the construction of a pBL1-free strain of B lactofermentum. Based on transformation efficiencies and plasmid stability, the resultant pBL1- free strain is more useful than wild strain as a host cell for genetic manipulation. It could be concluded that foreign plasmid DNAs are efficiently isolated and analyzed from the pBL1-free strain because of the absence of endogenous pBL1 plasmid.

• Journal of Microbiology and Biotechnology
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• v.3 no.4
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• pp.217-223
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• 1993

To investigate the nature and location of the nisin-resistance determinant of Lactococcus lactis subsp. lactis 7962 (L. lactis 7962), a total plasmid DNA prepared from L. lactis 7962, a nisin producer, was used to transform L. lactis subsp. lactis LM0230, a plasmid-free and nisin-sensitive strain, by protoplast mediated transformation procedures. All of the nisin-resistant transformants acquired the ability to utilize sucrose at the same time, confirming the close linkage between these two determinants in L. lactis 7962. The plasmid DNA profiles of a few selected nisin-resistant transformants were examined by agarose gel electrophoresis. No common plasmid was found among the transformants and some small plasmids previously not present in L. lactis 7962 were detected. These transformants were named as L. lactis KL1, KL2, KL3, KL4, or KL5, respectively based on their plasmid profiles. Growth curves of all transformants were similar to that of L. lactis LM0230, but different from that of L. lactis 7962. L. lactis KL5 showed the highest level of resistance to nisin, growing up to 1, 200 IU nisin/ml after 40 hr incubation. Some nisin-sensitive derivatives of KL1 or KL2 were obtained by plasmid curing experiments. The plasmid DNA profiles of the nisin-sensitive KL1 derivatives were apparently the same as that of the KL1. All of the nisin-sensitive KL2 derivatives were plasmid-free, but a nisin-resistant strain with no apparent plasmid was also obtained. These results indicate that the nisin-resistance of the $Nis^r$ transformants is presumably mediated by the chromosomally located gene(s) rather than plasmid-encoded gene(s).

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1025-1030
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• 2004

A hybrid linear polymer-dendrimer block copolymer, poly(ethylene glycol)-block-poly(L-lysine) dendrimer, was synthesized and introduced to form polyionic complexes with DNA. The copolymer formed core-shell type nanoparticles with plasmid DNA. From dynamic light scattering experiments, the mean diameter of the polyplexes was observed to be 154.4 nm. The complex showed much increased water solubility compared to poly(L-lysine). The plasmid DNA in polyplexes was efficiently protected from the enzymatic digestion of DNase I. The cytotoxicity and transfection efficiency for 293 cells was measured in comparison with poly(Llysine).