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Expression of the F plasmid ccd toxin–antitoxin system in Escherichia coli cells under nutritional stress

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The ccd system of the F plasmid encodes CcdB, a protein toxic to DNA-gyrase, and CcdA, its antitoxin. The function attributed to this system is to contribute to plasmid stability by killing bacteria that lose the plasmid during cell division. However, the function of ccd in resting bacteria is not clear. Results presented show that ccd transcription increases as bacteria enter stationary phase and that the amount of the Ccd proteins is higher in bacteria under nutritional stress than in growing bacteria. Moreover, an increase in the frequency of Lac+ "adaptive" mutations was observed in stationary-phase bacteria that over-express the Ccd proteins.Key words: ccd system, nutritional stress, adaptive mutation.

Le système ccd du plasmide F codifie pour CcdB, une protéine toxique pour le ADN-gyrase, et pour CcdA son antitoxine. La fonction attribuée à ce système est de contribuer à la stabilité du plasmide en tuant la bactérie qui perd le plasmide pendant la division cellulaire. Cependant, la fonction de ccd dans des bactéries au repos n'est pas claire. Les résultats que nous présentons montrent que la trancription de ccd augmente lorsque les bactéries entrent en phase stationnaire et que la quantité de protéines Ccd est plus importante dans les bactéries sous stress nutritionnel que dans les bactéries en croissance. De plus, un accroissement dans la fréquence de mutations de Lac+ "adaptive" a été observé dans des bactéries en phase stationnaire qui surexpriment les protéines Ccd.Mots clés : système ccd, stress nutritionnel, mutation adaptive.

Document Type: Research Article

Publication date: January 1, 2006

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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