Molecular mechanism of transcriptional cascade initiated by the EvgS/EvgA system in Escherichia coli K-12.

Using an EvgS-active mutant (evgS1) in combination with gene deletions, we clarified the molecular mechanism of the transcriptional cascade of acid resistance and multidrug resistance genes initiated by the EvgS/EvgA two-component system in Escherichia coli, followed by sequential induction of the transcriptional regulators, YdeO and GadE. Overexpression of EvgA, the response regulator of the EvgS/EvgA system, is known to induce the expression of a number of acid resistance and multidrug resistance genes, in which the EvgA-YdeO-GadE circuit is involved, but the role of the sensor EvgS in this circuit has remained unsolved. Our results suggest that the transcriptional cascade initiated by the EvgS/EvgA system in fact functions for acid and drug resistance in E. coli.