• Korean Journal of Microbiology
• /
• v.26 no.3
• /
• pp.173-180
• /
• 1988

Chromosomal gene transferable hybrid plasmids, RP4::Mu cts and RP4::mini-Mu, were transferred by conjugation from E. coli to Pseudomonas strains. In order to use for recipient cells of RP4::Mu cts and RP4:: mini-Mu, plasmid-free Pseudomonas strains were characterized for their antobiotic resistance, aromatic hydrocarbon utility and degradation patterns of chlorinated herbicide. Transfer frequencies of RP4::mini-Mu exhibited about $10^{-2}$ to $10^{-4}$, while those of RP4::Mu cts exhibited very low value of $10^{-7}$ in recipients tested except Pseudomonas aeruginosa KU557. Existance of hybrid plasmids in Pseudomonas transconjugants were identified by their antibiotic resistance and agarose gel electrophoresis. In case of RP4::Mu cts transconjugants it was also confirmed by demonstrating that they were capable of releasing phage and forming plaques at $43^{\circ}C$. Plaque forming unit of the transconjugants was about $10^{5}$. It was shown by the stability test that RP4::Mu cts and RP4::mini-Mu in Pseudomonas were relatively stable.

• Korean Journal of Microbiology
• /
• v.23 no.2
• /
• pp.107-114
• /
• 1985

In order to use for recipient strains of RP4:Mu cts, 5 strainsof Rhizobium were selected among 32 strains, which were isolated and identified in this study. Hybrid plasmin RP4::Mu cts, which, is temperature sensitive and confers resistance to ampicillin, kanamycin and tetracycline was transfered by conjugation from E. coli to other atrains of C. coli and the symbiotic nitrogen fixer, Rhizobium leguminosarum. Transfer frequencies of RP4::Mu cts plasmid from E. coli to Rhizobium were about $10^{-8}-10^{-7}$ in LB agar and YMA media. The transconjugants were confirmed by demonstrating that the drug-resistant and temperature-sensitive clones isolated were drug-resistant and temperature-sensitive clones isolated were capable of releasing phage and forming plaques. The plaque-forming units of transconjugants were about $10^2\;to\;10^3$. Stability test of RP4::Mucts in Rhizobium represented that most of the transconjugants had drug resistance and produce phage Mu cts.

• Korean Journal of Microbiology
• /
• v.24 no.3
• /
• pp.211-220
• /
• 1986

Nitrogen fixation (nif) genes of Rhizobium leguminosarum were transferred to nif Klebsiella pneumoniae and E. coli by conjugation after partial heat induction of $RP_4$ :: Mu cts in Rhizobium $R^+$ transconjugant, and the hybrid plasmids in the transconjugant strains were isolated and characterized. In order to transfer the nif genes from Rhizobium, the hybrid plasmid $RP_4$ :: Mu cts was transferred by conjugation from E. coil to the symbiotic nitrogen fixer, R. leguminosarum. After stabillity test, the $RP_4$ :: Mu cts in Rhixobium $R^+$ transconjugant was subjected to partial heat induction by culturing it statically at $38^{\circ}C$ for 16 hours, and then conjugated with the nif defective mutant strains of K. pneumoniae or nif mutant strains of E. coli having whole nif gene plasmid. Recombinant strains of K. pneumoniae, which could grow in a N-free medium and exhibit the nitrogenase activity were selected. However, in the case of E. coli, they could grow well in a NA medium containing antibiotices, but hardly frow in a N-free medium. The hybrid plasmids in these transconjugal strains were isolated by gel electrophoresis and compared their molecular sizes.