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Mol Microbiol. 1997 May;24(3):643-51.

The sigma S level in starving Escherichia coli cells increases solely as a result of its increased stability, despite decreased synthesis.

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Department of Microbiology and Immunology, School of Medicine, Stanford University, California 94305, USA.


The sigma S level in starving (stationary phase) Escherichia coli cells increases four-to sixfold following growth in a defined or a complex medium. Chemostat-grown cells, subjected to increasing carbon starvation, also become progressively richer in sigma S content. These increases occur despite reduced transcription of the sigma S-encoding gene, rpoS, and translation of rpoS mRNA, and result solely from a large increase in the stability of the sigma protein. Previous results, based on rpoS::lacZ transcriptional and translational fusions, and on methionine incorporation in sigma S, had suggested increased synthesis of sigma S in starving cells. Alternative explanations for these results consistent with the conclusions of this paper are discussed.

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