Regulation of ompF porin expression by salicylate in Escherichia coli

Abstract

The expression of ompF, the gene encoding a major outer membrane protein of Escherichia coli, is regulated by various environmental factors. The mechanism by which salicylate (SAL) drastically reduces ompF expression was studied here by means of lacZ fusions to ompF, ompC, and micF, by sodium dodecyl sulfate-gel electrophoresis of outer membrane proteins, and by measurements of outer membrane permeability. Growth of E. coli in LB broth containing SAL strongly reduced ompF-specific translation of an ompF-lacZ fusion. The extent of this reduction varied with the SAL concentration from 64% at 0.5 mM to 95% at 2 mM and >99% at 10 mM. ompF-lacZ transcription was not affected by SAL, whereas ompC-lacZ transcription was elevated by 70%. Since the micF transcript is antisense to a portion of the ompF transcript and is capable of decreasing the translation of ompF, the effect of SAL on micF transcription was measured in a micF-lacZ fusion strain. SAL-grown cells contained three-to fourfold more micF transcript during the logarithmic phase of growth than did the control cultures. However, micF was not absolutely required for the response to SAL. In micF-deleted strains, the effects of SAL on ompF translation, on OmpF in the outer membrane, and on outer membrane permeability were diminished but still evident. The effect of SAL on ompF expression was independent of the osmolarity of the medium and was epistatic to certain ompB regulatory mutations: the high levels of ompF expression found in envZ3 and ompR472 strains were greatly reduced by growth in SAL. Unexpectedly, the OmpC-phenotypes of these mutants were suppressed by SAL. Thus, growth in SAL severely decreases the translation of ompF while enhancing the transcription of micF and ompC. In this respect, SAL-grown cells resemble certain marA and toiC mutants that have high levels of micF and ompC transcripts and low levels of OmpF.

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

“…Regulation of porin expression also occurs in response to chemicals in the environment. It was found in 1991 that salicylate in the medium decreased OmpF synthesis (560). This is now known to be a part of the global regulation of porins mediated by three XylS-AraC family regulatory proteins, MarA, SoxS, and Rob (9,174).…”

Kinetic behavior of the major multidrug efflux pump AcrB of Escherichia coli

“…We thus used cells in early stationary phase (36). With cefazolin, OmpF was further repressed by adding 5 mM sodium salicylate to the medium (37). Cells were grown at 30°C (except for cephaloridine) because this appeared to improve the expression of the TEM ␤-lactamase in strain HN1160.…”

Salicylate increases the expression of marA and reduces in vitro biofilm formation in uropathogenic Escherichia coli by decreasing type 1 fimbriae expression

“…Salicylate inhibits the binding of MarR to mar operator region of the mar operon which then leads to increased production of MarA and a decrease in antibiotic accumulation associated with a reduction in the production of the outer membrane porins OmpF and OmpC and to a concomitant increase in the production of the multidrug efflux pump AcrAB. 12,13 MarA expression is also involved in the virulence of E. coli. Using a murine model of pyelonephritis, Casaz et al 14 observed that strains lacking this gene were unable to maintain colonization of the kidney.…”