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

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.