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Journal of Bacteriology, August 1998, p. 3917-3922, Vol. 180, No. 15
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Regulation of Porin-Mediated Outer Membrane Permeability by Nutrient Limitation in Escherichia coli

XueQiao Liu and Thomas Ferenci*

Department of Microbiology, University of Sydney, Sydney, New South Wales 2006, Australia

Received 30 March 1998/Accepted 30 May 1998

OmpF and OmpC porins were differentially regulated by nutrient limitation and growth rate in glucose- or nitrogen-limited chemostat cultures of Escherichia coli. Transcriptional and translational ompF fusions showed a sharp peak of expression under glucose limitation at D = 0.3 h-1, with lower amounts at lower and higher growth rates. The peak of OmpR-dependent transcriptional stimulation of ompF under glucose limitation in minimal salts media was about 20-fold above nutrient excess levels and 3-fold higher than that achieved with low osmolarity. Analysis of outer membrane protein levels and results of growth competition experiments with porin mutants were consistent with the enhanced role of OmpF under glucose limitation, but not N limitation. In contrast, OmpC was the major porin under N limitation but was increasingly expressed under glucose limitation at very low growth rates approaching starvation, when OmpF was downregulated. In summary, outer membrane permeability under N-limited, sugar-rich conditions is largely based on OmpC, whereas porin activity is a complex, highly sensitive function of OmpF, OmpC, and LamB glycoporin expression under different levels of glucose limitation. Indeed, the OmpF level was more responsive to nutrient limitation than to medium osmolarity and suggested a significant additional layer of control over the porin-regulatory network.

* Corresponding author. Mailing address: Department of Microbiology, G08, University of Sydney, Sydney, N.S.W. 2006, Australia. Phone: 61-2-9351 4277. Fax: 61-2-9351-4571. E-mail: t.ferenci{at}microbio.su.oz.au.

Journal of Bacteriology, August 1998, p. 3917-3922, Vol. 180, No. 15
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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