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Biomedical subjects

J Hubácek

Publications and source records attributed to J Hubácek.

At least 73 records · Page 4Linked to original sources
PubMed1983

The instability of plasmid pON5300 after its transformation into Escherichia coli K 12.

The plasmid R1drd-19 Km- and its derivative pON5300 were split by the PstI restriction enzyme; they differed in a 2.4 Mg/mol fragment which was present only in the pON5300. Both plasmids were present in 1-2 copies per chromosomal equivalent in E. coli JC5455 cells. The pON5300 is stable in its original mutagenized host but it segregates the enlarged region of the plasmid molecule after transformation into non-mutagenized E. coli JC5455. The possible explanation of this instability is discussed.

Anti-Bacterial Agents↗
PubMed1983

Stability of the hybrid plasmid pIM138 and its curing by some eliminating agents.

Hybrid plasmid pIM138 was constructed by insertion of a chromosomal fragment with the threonine operon from Escherichia coli into the pBR322 vector. Molar mass of pIM138 was 2.8 Mg/mol. Heteroduplexes between pBR322 vector and pIM138 hybrid DNA molecules were prepared. The hybrid plasmid shows a high stability against the curing effect of rifampicin and clorobiocin in E. coli SK1590 thr host.

Chromosomes, Bacterial↗
PubMed1982

Trans-dominant mutation affecting restriction and modification in Escherichia coli K-12.

We have analysed the mechanism of action of a ts mutation in E. coli, which has an effect on the expression of the restriction and modification phenotype. The frequencies of recombinants obtained in transduction experiments support the idea that the temperature sensitive mutation is located outside the hsd operon in the gene denoted hsd.X. Complementation experiments demonstrated the trans-dominant nature of the temperature sensitive mutation. The possible role of the hsd.X product in the formation of EcoR.K and EcoM.K complexes and their interaction with the recognition site on the DNA is discussed.

Bacteriophage lambda↗
PubMed1982

Curing effect of clorobiocin on Escherichia coli plasmids.

Clorobiocin, an inhibitor of the gyrB subunit of DNA gyrase, was used for the curing of some Escherichia coli plasmids. Of the plasmids studied, ampicillin resistant R28K and a miniplasmid derived from R1drd-19 were effectively eliminated. We also succeeded in eliminating the ColA factor from E. coli strain B834(pBS103), which was resistant to the effect of currently used curing agents. Although a derivative of ColE1-pBR322 was effectively cured by clorobiocin, the ColE1 plasmid was resistant to its effect. The ColV plasmid determining virulence was effectively eliminated.

Ampicillin↗
PubMed1982

The recA-dependent spontaneous degradation of proximal F merogenotes in Escherichia coli.

Proximal F' elements of KLF-1 type are relatively stable in Escherichia coli recA recipients. In such merodiploids the transferability of F'-DNA and the plasmid determined fertility functions are expressed. When introduced into the wild type recA+ cells the F'-DNA is degraded and several classes of DNA molecules of molar mass about 66 Mg/mol and lower exist in the cell in 1-2 copies per bacterial chromosome. As was detected by complementation analysis, the chromosomal genes determining the host specificity for DNA (hsd) originally located on the F' element seem to be salvaged during the process of DNA degradation probably by recombination with the bacterial chromosome.

Bacterial Proteins↗
PubMed1981

Physical characterization of the plasmid pON5300.

The antibiotic resistance plasmid R1drd19Km- which has spontaneously lost its kanamycin resistance marker, and its derivative pON5300, were analysed using the restriction endonucleases SalI, BamHI, HindIII and EcoRI. The fragment patterns were compared with that of the R1drd19 and the fragments responsible for kanamycin resistance were found to be missing in R1drd19Km- and pON5300. In these plasmids a 7 Mg/mol EcoRI fragment was observed instead of the D (6.3 Mg/mol) fragment of R1drd19. Further a new 6 Mg/mol EcoRI restriction fragment was observed in pON5300. Using double digestions it was shown that the new fragment does not carry restriction sites for HindIII, BamHI and SalI endonucleases. The non-homology of the analysed plasmid was proved electron microscopically by heteroduplex techniques. The possibility of amplification in the regulatory region for the expression of R-determinants in pON5300 is discussed.

DNA Restriction Enzymes↗