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Front. Microbiol. | doi: 10.3389/fmicb.2018.02656

A new role for OmpR in acid and osmotic stress in Salmonella and E. coli

  • 1Singapore Bioimaging Consortium (A*STAR), Singapore
  • 2Mechanobiology Institute, National University of Singapore, Singapore
  • 3University of Illinois at Chicago, United States
  • 4Jesse Brown VA Medical Center, United States

Bacteria survive and respond to diverse environmental conditions and during infection inside the host by systematic regulation of stress response genes. E. coli and S. Typhimurium can undergo large changes in intracellular osmolality (up to 1.8 Osmol/kg) and can tolerate cytoplasmic acidification to at least pHi 5.6. Recent analyses of single cells challenged a long held view that bacteria respond to extracellular acid stress by rapid acidification followed by a rapid recovery. It is now appreciated that both S. Typhimurium and E. coli maintain an acidic cytoplasm through the actions of the outer membrane protein regulator OmpR via its regulation of distinct signaling pathways. However, a comprehensive comparison of OmpR regulons between S. Typhimurium and E. coli is lacking. In this study, we examined the expression profiles of wild-type and ompR null strains of the intracellular pathogen S. Typhimurium and a commensal E. coli in response to acid and osmotic stress. Herein, we classify distinct OmpR regulons and also identify shared OmpR regulatory pathways between S. Typhimurium and E. coli in response to acid and osmotic stress. Our study establishes OmpR as key regulator of bacterial virulence, growth and metabolism, in addition to its role in regulating outer membrane proteins.

Keywords: single cells, OmpR, acid stress, osmotic stress, i-Switch, fluorescence microscopy, BCECF, GltA, CAD, GAD, rpoS, Two-component regulatory system, EnvZ

Received: 16 Jul 2018; Accepted: 17 Oct 2018.

Edited by:

Daniela De Biase, La Sapienza University of Rome, Italy

Reviewed by:

Sylvie RIMSKY, UMR7241 Centre interdisciplinaire de recherche en biologie (CIRB), France
Peter A. Lund, University of Birmingham, United Kingdom
Samantha Miller, University of Aberdeen, United Kingdom  

Copyright: © 2018 Chakraborty and Kenney. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Linda J. Kenney, Mechanobiology Institute, National University of Singapore, Singapore, Singapore, kenneyl@uic.edu