It was previously demonstrated that the intestinal pathogen Vibrio cholerae
could undergo an adaptive stress response known as the acid tolerance resp
onse (ATR). The ATR is subdivided into two branches, inorganic ATR and orga
nic ATR. The transcriptional regulator ToxR, while not involved in inorgani
c ATR, is required for organic ATR in a ToxT-independent manner. Herein, we
investigate the effect of organic acid stress on global protein synthesis
in V. cholerae and show by two-dimensional gel electrophoresis that the str
ess response alters the expression of more than 100 polypeptide species. Th
e expression of more than 20 polypeptide species is altered in a toxR strai
n compared to the wild type. Despite this, ectopic expression of the porin
OmpU from an inducible promoter is shown to be sufficient to bypass the tox
R organic ATR defect. Characterization of the effect of organic acid stress
on ompU and ompT transcription reveals that while ompU transcription remai
ns virtually unaffected, ompT transcription is repressed in a ToxR-independ
ent manner. These transcript levels are similarly reflected in the extent o
f accumulation of OmpU and OmpT, Possible roles for OmpU in organic acid re
sistance are discussed.