RpoS sigma factor mediates adaptation and virulence in Vibrio mimicus

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• The alternative sigma factor RpoS regulates stress and virulence in bacteria.
• Vibrio mimicus is an opportunistic pathogen impacting aquaculture.
• The specific role of RpoS in V. mimicus was previously unknown.

Purpose of the Study:

• To elucidate the function of RpoS in Vibrio mimicus.
• To investigate the phenotypic and transcriptional consequences of rpoS deletion.

Main Methods:

• Construction of an rpoS deletion mutant (ΔrpoS) via allelic exchange.
• Phenotypic analysis of growth, motility, biofilm production, hemolytic activity, and pathogenicity.
• Assessment of stress tolerance (H₂O₂, heat, ethanol, starvation) in stationary-phase cells.
• Transcriptome analysis (RNA-seq) to identify RpoS-regulated genes.
• β-galactosidase assays to confirm transcriptional regulation of specific genes (flgK, fliA, cheA, mcpH).

Main Results:

• The ΔrpoS strain exhibited significantly impaired growth, motility, biofilm formation, hemolytic activity, and pathogenicity.
• Stationary-phase ΔrpoS cells showed reduced tolerance to oxidative, thermal, ethanol, and starvation stresses compared to wild-type.
• RNA-seq revealed RpoS involvement in flagellar synthesis, membrane processes, and response to stimuli.
• RpoS is essential for the transcription of key genes involved in motility and signaling (flgK, fliA, cheA, mcpH).

Conclusions:

• RpoS is a critical regulator of biofilm formation, stress resistance, and pathogenicity in Vibrio mimicus.
• RpoS controls essential cellular processes including flagellar assembly and membrane functions.
• Understanding the RpoS regulatory network provides insights for developing prevention strategies against V. mimicus.