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Spatiotemporal Variations in Growth Rate and Virulence Plasmid Copy Number during Yersinia pseudotuberculosis

Stephan Schneiders1, Tifaine Hechard1, Tomas Edgren1

  • 1Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.

Infection and Immunity
|January 26, 2021
PubMed

Insights

Pathogenic Yersinia bacteria increase virulence plasmid copy number (PCN) during infection for enhanced type 3 secretion system (T3SS) function. This study tracked bacterial growth and PCN dynamics in mouse organs, revealing tissue-specific adaptations.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Bacterial Pathogenesis

Background:

  • Pathogenic Yersinia species utilize a type 3 secretion system (T3SS) encoded on a virulence plasmid for host colonization.
  • Yersinia pseudotuberculosis upregulates virulence plasmid copy number (PCN) during infection, increasing the gene dose of T3SS components, which is crucial for virulence.

Purpose of the Study:

  • To investigate the dynamics of Yersinia pseudotuberculosis virulence plasmid copy number (PCN) and bacterial growth rates in infected mouse organs.
  • To understand when and how the upregulation of virulence plasmid replication is regulated during infection.

Main Methods:

  • Droplet digital PCR (ddPCR) was employed to quantify Yersinia pseudotuberculosis virulence PCN variations.
  • Bacterial growth rates and loads were assessed in various infected mouse tissues over time.

Main Results:

  • Both PCN and bacterial growth rates varied significantly across different tissues and time points during infection.
  • Highest PCN was observed in Peyer's patches and the cecum during the invasive phase, while peak growth rates occurred in mesenteric lymph nodes.
  • Systemic organs showed lower PCN and more moderate growth rates.

Conclusions:

  • Increased gene dosage of T3SS genes via elevated PCN is most critical during the early, invasive stages of Yersinia infection.
  • Bacterial populations adapt to distinct microenvironments within host organs, influencing both PCN and growth.
  • The ddPCR method provides a simplified approach for analyzing PCN, growth dynamics, and bacterial loads in infection models.
Keywords:
Yersinia pseudotuberculosisbacterial growth rate in tissuesddPCRplasmid copy numbertype III secretion system

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