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Regulatory mechanism for host-cell contact-dependent T3SS gene expression in Vibrio parahaemolyticus

Sarunporn Tandhavanant1,2, Hiroyuki Terashima1,3, Hirotaka Hiyoshi1

  • 1Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.

Msystems
|June 17, 2025
PubMed

Insights

Vibrio parahaemolyticus uses a Type III Secretion System 2 (T3SS2) to sense host cell contact. This triggers the secretion of VtrN, a protein that represses virulence gene expression, enhancing bacterial infection strategies.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Pathogenesis

Background:

  • Pathogenic bacteria adapt gene expression to their environment for infection.
  • Host-cell contact is a critical environmental cue that triggers bacterial virulence gene regulation.
  • Type III secretion systems (T3SS) are essential virulence factors in many bacterial pathogens, requiring precise regulation.

Purpose of the Study:

  • To elucidate the host-cell contact-dependent regulatory mechanism of virulence gene expression in Vibrio parahaemolyticus.
  • To identify the specific components involved in sensing host-cell contact and modulating virulence factor production.
  • To understand how Vibrio parahaemolyticus adapts its virulence strategy upon interaction with host cells.

Main Methods:

  • Transcriptomic analysis of T3SS2 gatekeeper mutants.
  • Comparative proteomic analysis to identify novel T3SS2 substrates.
  • Gene deletion and interaction studies to characterize the function of VtrN.
  • Bacterial culture under conditions mimicking host-cell contact.

Main Results:

  • Vibrio parahaemolyticus utilizes T3SS2 to sense host-cell contact via intracellular K+ levels, switching secretory substrates.
  • A novel T3SS2 substrate, VtrN, was identified as a negative regulator of Vp-PAI (virulence gene cluster) transcription.
  • VtrN secretion is promoted upon host-cell contact, and its deletion upregulates Vp-PAI expression.
  • VtrN directly interacts with the transcription factor VtrB, suppressing Vp-PAI gene activity.

Conclusions:

  • Vibrio parahaemolyticus employs a sophisticated T3SS2-mediated mechanism to upregulate virulence gene expression upon host-cell contact.
  • The secreted protein VtrN acts as a crucial repressor, linking host-cell sensing to the control of virulence gene transcription.
  • This adaptive strategy allows V. parahaemolyticus to optimize its virulence factor production during host infection, providing insights into bacterial pathogenesis.
Keywords:
Vibrio parahaemolyticusgatekeepergene regulationtype III secretion system

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