Article Abstract:
The effect of abiotic and biotic factors on the number of transconjugant formed and the transfer frequency during plasmid transfer between Eschericia coli strains was determined. The results showed that the density of parents cells and the total organic (TOC) affected the number of transconjugants. In addition, TOC also affected the transfer frequency. However, there were no variations in both the number of transconjugants and transfer frequency resulting from the differences in pH, mating temperature and mating time.
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Article Abstract:
The plasmid transfer rate constant of the conjugative plasmid R388:Tn1721 going from Pseudomonas cepacia to P. fluorescens appears to be dependent on parental cell density when parental growth is limited. Plasmid transfer was examined at three different parental cell densities in agar, broth, and sterile or nonsterile soil microcosms with or without germinating pea seeds. The findings suggested that competition may limit parental growth and thus reduce the transfer rate.
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Article Abstract:
The recognition of nitroaromatics as substrates by TOL plasmid upper-pathway enzymes was discussed. The study showed that the expression of xylMA genes that encode for toluene monoxygenase resulted in the oxidation of toluene and m- and p-nitrotoluene to benzyl alcohols and benzaldehydes in Pseudomonas putida and Escherichia coli. However, the XylR protein did not recognized nitrosubstituted toluenes as effectors.
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