Characterization of mutations in the PAS domain of the EvgS sensor kinase selected by laboratory evolution for acid resistance in Escherichia coli

Research output: Contribution to journalArticlepeer-review


  • Matthew D. Johnson
  • James Bell
  • Kim Clarke
  • Rachael Chandler
  • Prachi Pathak
  • Yandong Xia
  • George M. Weinstock

Colleges, School and Institutes

External organisations

  • State Key Laboratory of Microbial Technology; Shandong University; 27 Shanda Southern Road Jinan China
  • The Genome Institute; Washington University School of Medicine; St. Louis MO 63108 USA
  • The Jackson Laboratory for Genomic Medicine; Farmington CT 06030 USA
  • School of Biosciences, University of Birmingham


Laboratory-based evolution and whole-genome sequencing can link genotype and phenotype. We used evolution of acid resistance in exponential phase Escherichia coli to study resistance to a lethal stress. Iterative selection at pH 2.5 generated five populations that were resistant to low pH in early exponential phase. Genome sequencing revealed multiple mutations, but the only gene mutated in all strains was evgS, part of a two-component system that has already been implicated in acid resistance. All these mutations were in the cytoplasmic PAS domain of EvgS, and were shown to be solely responsible for the resistant phenotype, causing strong upregulation at neutral pH of genes normally induced by low pH. Resistance to pH 2.5 in these strains did not require the transporter GadC, or the sigma factor RpoS. We found that EvgS-dependent constitutive acid resistance to pH 2.5 was retained in the absence of the regulators GadE or YdeO, but was lost if the oxidoreductase YdeP was also absent. A deletion in the periplasmic domain of EvgS abolished the response to low pH, but not the activity of the constitutive mutants. On the basis of these results we propose a model for how EvgS may become activated by low pH.


Original languageEnglish
Pages (from-to)911–927
JournalMolecular Microbiology
Issue number5
Early online date24 Jul 2014
Publication statusPublished - 29 Aug 2014