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σ E controlled regulation of porin OmpU in Vibrio cholerae
Author(s) -
Pennetzdorfer Nina,
Höfler Thomas,
Wölflingseder Martina,
Tutz Sarah,
Schild Stefan,
Reidl Joachim
Publication year - 2021
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14669
Subject(s) - biology , porin , vibrio cholerae , regulon , microbiology and biotechnology , bacterial outer membrane , virulence , vibrionaceae , cholera toxin , enterobacteriaceae , response regulator , bacteria , transcription factor , genetics , gene , escherichia coli , bacterial protein
Bile resistance is essential for enteric pathogens, as exemplified by Vibrio cholerae , the causative agent of cholera. The outer membrane porin OmpU confers bacterial survival and colonization advantages in the presence of host‐derived antimicrobial peptides as well as bile. Expression of ompU is controlled by the virulence regulator ToxR. rpoE knockouts are accompanied by suppressor mutations causing ompU downregulation. Therefore, OmpU constitutes an intersection of the ToxR regulon and the σ E ‐pathway in V . cholerae . To understand the mechanism by which the sigma factor σ E regulates OmpU synthesis, we performed transcription studies using ompU reporter fusions and immunoblot analysis. Our data revealed an increase in ompU promoter activity in Δ rpoE strains, as well as in a Δ ompU background, indicating a negative feedback regulation circuit of ompU expression. This regulation seems necessary, since elevated lethality rates of Δ rpoE strains occur upon ompU overexpression. Manipulation of OmpU’s C‐terminal portion revealed its relevance for protein stability and potency of σ E release. Furthermore, Δ rpoE strains are still capable of elevating OmpU levels under membrane stress conditions triggered by the bile salt sodium deoxycholate. This study provides new details about the impact of σ E on ompU regulation, which is critical to the pathogen’s intestinal survival.