The pcnB gene sustains Shigella flexneri virulence.

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Shigella flexneri utilizes a Type Three Secretion System (T3SS) for intestinal colonization.
• T3SS genes reside on the pINV virulence plasmid, and their expression is tightly regulated.
• T3SS expression impacts Shigella growth, necessitating a balance between virulence and replication.

Purpose of the Study:

• Investigate the role of the chromosomal gene pcnB, encoding poly-A polymerase I (PAP-I), in Shigella flexneri pathogenesis.
• Determine how pcnB influences T3SS expression, virulence plasmid replication, and bacterial growth.
• Elucidate the mechanisms by which pcnB contributes to Shigella colonization and infection.

Main Methods:

• Genome-wide screening to identify host factors affecting Shigella.
• Growth curve analysis of Shigella strains at 37°C.
• Proteomic profiling to assess global changes in gene expression.
• Enteroid model colonization assays to evaluate early infection dynamics.
• Analysis of pINV plasmid replication and antisense RNA CopA levels.

Main Results:

• The pcnB gene slows Shigella growth at 37°C but promotes early colonization of human enteroids.
• pcnB significantly upregulates the Shigella T3SS virulence program.
• pcnB sustains pINV plasmid replication by increasing degradation of the antisense RNA CopA.
• pcnB-mediated pINV maintenance supports longer-term intraepithelial expansion post-invasion.

Conclusions:

• pcnB is a key regulator linking bacterial growth, virulence plasmid replication, and T3SS expression in Shigella flexneri.
• Adequate pINV levels, maintained by pcnB, are crucial for successful Shigella infection cycle execution.
• pcnB represents a potential target for therapeutic strategies against Shigella infections.