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Journal of Bacteriology, February 2000, p. 956-960, Vol. 182, No. 4
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Genetic Evidence of Distinct Physiological Regulation Mechanisms in the sigma 54 Pu Promoter of Pseudomonas putida

Ildefonso Cases and Víctor de Lorenzo*

Centro Nacional de Biotecnología CSIC, 28049 Madrid, Spain

Received 24 September 1999/Accepted 24 November 1999

The activity of the toluene-responsive sigma 54 Pu promoter of the pWW0 TOL plasmid of Pseudomonas putida is down-regulated in vivo during exponential growth in rich medium and also by the presence of glucose in the culture. Although the Pu promoter already performs poorly during log growth in minimal medium when amended with casamino acids, the addition of glucose further decreased by two- to threefold the accumulation of beta -galactosidase in a Pu-lacZ reporter P. putida strain. Since Pu was still down-regulated during exponential growth regardless of glucose addition, it appeared that the carbohydrate separately influenced promoter activity. This notion was supported by the growth-dependent induction pattern of Pu in a ptsN mutant of P. putida, the loss of which makes Pu no longer responsive to repression by glucose. On the other hand, overexpression of the sigma factor sigma 54, known to partially alleviate the exponential silencing of the promoter, did not affect glucose inhibition of Pu. These data indicated that exponential silencing and carbon source-dependent repression are two overlapping but genetically distinguishable mechanisms that adapt Pu to the physiological status of the cells and nutrient availability.

* Corresponding author. Mailing address: Centro Nacional de Biotecnología CSIC, Campus de Cantoblanco, 28049 Madrid, Spain. Phone: 34 91 585 4536. Fax: 34 91 585 4506. E-mail: vdlorenzo{at}cnb.uam.es.

Journal of Bacteriology, February 2000, p. 956-960, Vol. 182, No. 4
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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