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Integration of F’<em>lac</em> plasmid into chromosome of both <em>gyrA</em>(Ts) and <em>gyrB</em>(Ts) cells phenotypically suppress the thermosensitive mutations of the DNA gyrase enzymes. As the comparative strains isolated from <em>dnaA</em>(Ts), these high frequency of recombination (Hfr) derivatives were able to transfer chromosomal markers to recipient strains, showed a growth rate of about 60 min, and developed filamentous forms when incubated at the temperature of 43°C. Conversely to <em>dnaA</em>(Ts) Hfr selected isolates, the great majority of Hfr derivative of gyrase mutants resulted resistant to acridine orange and rifampin. Time-kill experiments carried out at the non-permissive temperature also revealed that nalidixic acid has no antibacterial activity on these Hfr strains while derivatives of <em>dnaA</em>(Ts) mutant, as well as the control strain HfrH, were strongly inhibited by this drug. Therefore F plasmid induced duplication of chromosome in the mutants even if the DNA gyrase enzymes are not working. Of a certain interest is that these bacteria exhibit physiological perturbations that affect the main cellular functions, however, they do not appear essential for the survival of the strains.