Enhanced expression of the bgl operon of Escherichia coli in the stationary phase.

The bgl operon is silent and uninducible in wild-type strains of Escherichia coli and requires mutational activation for optimal expression. We show that transcription from the wild-type and the activated bgl promoter exhibits a growth phase-dependent enhancement that is highest in the stationary phase. We have assessed the effect of mutations in rpoS, crl, hns, leuO and bglJ, known to regulate bgl expression, on the growth phase-dependent increase in bgl activity.

Mutations that activate the silent bgl operon of Escherichia coli confer a growth advantage in stationary phase.

Wild-type strains of Escherichia coli are unable to utilize aromatic beta-glucosides such as arbutin and salicin because the major genetic system that encodes the functions for their catabolism, the bgl operon, is silent and uninducible. We show that strains that carry an activated bgl operon exhibit a growth advantage over the wild type in stationary phase in the presence of the rpoS819 allele that causes attenuated rpoS regulon expression. Our results indicate a possible evolutionary advantage in retaining the silent bgl operon by wild-type bacteria.