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Related Concept Videos

Bacterial Toxins01:12

Bacterial Toxins

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Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...
34

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Related Experiment Video

Updated: Mar 28, 2026

Cefoperazone-treated Mouse Model of Clinically-relevant Clostridium difficile Strain R20291
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Increased toxin expression in a Clostridium difficile mfd mutant.

Stephanie E Willing1,2, Emma J Richards3, Lluis Sempere4

  • 1Department of Life Sciences, Centre for Molecular Bacteriology and Infection, Imperial College London, London, SW7 2AZ, UK. Stephanie.Willing@rhul.ac.uk.

BMC Microbiology
|December 19, 2015
PubMed
Summary
This summary is machine-generated.

The Mfd protein is a novel regulator of toxin production in Clostridium difficile. Inactivating mfd significantly increases toxin A and B expression and cytotoxicity, impacting infection severity.

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • Clostridium difficile infection symptoms are primarily caused by TcdA and TcdB toxins.
  • Toxin expression is influenced by nutrient availability, growth phase, cell stress, and global regulators like CcpA and CodY.

Purpose of the Study:

  • To investigate the role of the mfd gene in regulating toxin expression in Clostridium difficile.
  • To characterize the effects of mfd inactivation on toxin production and cytotoxicity.

Main Methods:

  • Generating insertion mutants in Clostridium difficile.
  • Analyzing colony morphology.
  • Marker recovery to identify gene insertions.
  • Western blotting and cytotoxicity assays.
  • Quantitative reverse transcription PCR (qRT-PCR).
  • Complementation studies using a plasmid-encoded mfd gene.

Main Results:

  • An off-target insertion in the mfd gene resulted in a branched colony morphology.
  • The mfd mutant showed significantly increased expression of both TcdA and TcdB toxins.
  • Cytotoxicity assays revealed at least a 10-fold increase in cell-killing activity in the mfd mutant.
  • qRT-PCR confirmed toxin upregulation at the transcriptional level.
  • Complementation restored wild-type phenotype, confirming mfd's role.

Conclusions:

  • Mfd is identified as a new factor involved in regulating toxin expression in Clostridium difficile.
  • The Mfd protein's function in resolving stalled RNA polymerase is crucial for preventing toxin de-repression.
  • Inefficiency in this process within the mfd mutant leads to consistently high toxin levels and increased pathogenicity.