Related Experiment Video
Updated: Jul 2, 2026
07:43
Coincubation Assay for Quantifying Competitive Interactions between Vibrio fischeri Isolates
Published on: July 22, 2019
Modulation of Vibrio cholerae porin function by acidic pH
Guillaume Duret1, Valérie Simonet, Anne H Delcour
1Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001, USA.
Channels (Austin, Tex.)
|August 12, 2008
Summary
Acidic conditions trigger pH-dependent closures in Vibrio cholerae OmpU porins, decreasing channel activity. OmpT porins remain unaffected, suggesting distinct roles in bacterial adaptation to host environments.
Area of Science:
- Microbiology
- Biophysics
- Structural Biology
Background:
- Gram-negative bacteria outer membranes utilize porins for nutrient transport.
- Vibrio cholerae, the cholera pathogen, faces environmental challenges like low pH during infection.
- OmpU and OmpT porins are implicated in V. cholerae's adaptation to host conditions.
Purpose of the Study:
- To investigate the impact of pH on the channel properties of OmpU and OmpT porins from Vibrio cholerae.
- To elucidate the role of these porins in bacterial adaptation to acidic environments.
Main Methods:
- Patch clamp electrophysiology.
- Planar lipid bilayer reconstitution assays.
- Analysis of porin channel gating and conductance at varying pH levels.
Main Results:
- OmpT activity remained stable across a pH range of 4 to 7.2.
- Acidic pH induced single-step closures in OmpU, increasing in duration and frequency as pH decreased.
- OmpU closures showed increased current size but unchanged overall trimeric conductance, suggesting coordinated gating.
Conclusions:
- OmpU exhibits pH-sensitive gating, contributing to V. cholerae's adaptation to acidic environments.
- The observed coordinated gating in OmpU suggests complex regulatory mechanisms within the porin trimer.
- Distinct pH-dependent behaviors of OmpU and OmpT highlight their specialized roles in V. cholerae pathogenesis.
Related Concept Videos
01:25Cholera
Cholera is an acute gastrointestinal disease caused by the Gram-negative bacterium Vibrio cholerae. It is transmitted primarily via the fecal-oral route through the ingestion of contaminated water or food.Vibrio cholerae is a motile, Gram-negative bacterium of the family Vibrionaceae, primarily associated with waterborne outbreaks in areas with inadequate sanitation. Although over 200 serogroups of V. cholerae exist, only O1 and O139 are responsible for epidemic cholera. The O1 serogroup,...
01:28pH Regulation in Cells
pH plays a critical role in maintaining normal cellular activities. It helps maintain the structure and function of various proteins, dictates the charge on cellular membranes, and is crucial for metabolic reactions inside the cell. Moreover, cells use the energy from the proton motive force to generate ATP.
Cytosolic pH
Under physiological conditions, the cytosolic pH is slightly more acidic than the extracellular pH. However, cells must prevent further acidification of their cytosol to...
Cytosolic pH
Under physiological conditions, the cytosolic pH is slightly more acidic than the extracellular pH. However, cells must prevent further acidification of their cytosol to...
01:28Regulation of Bacterial Virulence
Pathogenic bacteria employ a range of regulatory mechanisms to modulate the expression of virulence genes in response to environmental and host-derived signals. These mechanisms ensure that virulence factors are expressed only under favorable conditions, thereby optimizing infection and survival strategies.Mechanisms of Virulence RegulationKey regulatory strategies include:Two-Component Systems: These consist of a membrane-bound sensor kinase and a cytoplasmic response regulator. Environmental...
01:29Factors Influencing Microbial Growth: pH
Microorganisms are classified as acidophiles, neutrophiles, or alkaliphiles based on their pH growth preferences, reflecting their adaptations to specific environments. Maintaining a stable intracellular pH is critical for macromolecular stability and enzymatic activity, which can be challenged by external pH variations.Neutrophiles, such as Escherichia coli, grow optimally between pH 5.5 and 8.0. These microorganisms inhabit neutral or slightly acidic environments and employ mechanisms like...
01:09GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
Two...
01:21Structure of Porins
Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...