Expression and loss of the pBR322 plasmid in Klebsiella aerogenes NCTC 418, grown in chemostat culture |
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Authors: | A Sterkenburg G A P Prozée P A J Leegwater J T M Wouters |
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Institution: | (1) Laboratorium voor Microbiologie, Universiteit van Amsterdam, Nieuwe Achtergracht 127, 1018 WS Amsterdam, The Netherlands |
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Abstract: | Klebsiella aerogenes harbouring the plasmid pBR322 was grown in continuous culture at various growth rates under glucose, phosphate or ammonia limitation. With tetracycline in the medium, the maximum culture -lactamase activity was found at the higher growth rates. When tetracycline was absent, loss of resistance to the drug occurred. Concomitant with the occurrence of drug-sensitive cells, the culture -lactamase activity decreased. At the higher growth rates the enzyme activity decreased at a slightly higher rate than did the resistance to tetracycline. From this it was concluded that the -lactamase activity per mg cellular dry weight of the drug-resistant fraction of the population was still decreasing during the appearance of drug-sensitive cells. At the higher growth rates, this decrease was independent of the nutrient that was growth-limiting. |
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