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Updated: Jan 20, 2026

Visualization of Bacterial Toxin Induced Responses Using Live Cell Fluorescence Microscopy
Published on: October 1, 2012
Alternate subunit assembly diversifies the function of a bacterial toxin.
Casey C Fowler1,2, Gabrielle Stack1, Xuyao Jiao1
1Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, 06536, USA.
Salmonella Typhi produces two forms of typhoid toxin with distinct delivery components but shared active subunits. This toxin evolution offers functional versatility, revealing a new paradigm in bacterial toxin biology.
Area of Science:
- Microbiology
- Molecular Biology
- Toxinology
Background:
- Bacterial toxins often feature an AB5 architecture with active (A) and delivery (B) subunits.
- Salmonella Typhi, the causative agent of typhoid fever, produces a unique A2B5 typhoid toxin.
Purpose of the Study:
- To investigate the distinct forms and functions of typhoid toxin produced by Salmonella Typhi during human cell infection.
- To elucidate the evolutionary plasticity and functional versatility of AB5 toxins.
Main Methods:
- Analysis of typhoid toxin structure and subunit composition.
- Investigation of toxin trafficking properties in human cells.
- Assessment of toxin effects in laboratory animals.
- Examination of toxin gene regulation and metabolic cues.
Main Results:
- S. Typhi produces two typhoid toxin variants with different B subunits but common A subunits.
- These variants exhibit distinct cellular trafficking and differential effects in animal models.
- Expression of the two toxin forms is regulated by different mechanisms and metabolic signals.
Conclusions:
- The evolution of two typhoid toxin variants enhances functional versatility for Salmonella Typhi.
- This finding presents a new paradigm in toxin biology, highlighting structural plasticity in AB5 toxin evolution.
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