Role of sigma factor RpoS in Cronobacter sakazakii environmental stress tolerance

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Food Safety

Background:

• Cronobacter sakazakii is a foodborne pathogen often found in infant formula.
• This bacterium exhibits significant resistance to environmental stressors.
• The RpoS sigma factor is known to regulate bacterial stress responses.

Purpose of the Study:

• To investigate the role of the RpoS sigma factor in Cronobacter sakazakii.
• To determine how rpoS deficiency affects bacterial stress tolerance and cell properties.
• To elucidate the molecular mechanisms underlying RpoS-mediated stress resistance.

Main Methods:

• Construction of an rpoS-deficient mutant (Δrpos) of C. sakazakii BAA894 using Red homologous recombination.
• Comparative analysis of membrane formation, cell wall properties, and auto-aggregation between wild-type and mutant strains.
• Assessment of tolerance to acid, osmotic pressure, desiccation, and antimicrobial drugs.
• Transcriptome analysis to identify differentially expressed genes and altered metabolic pathways.

Main Results:

• The Δrpos mutant showed altered membrane formation, enhanced auto-aggregation, and modified motility.
• Acid and hyperosmotic resistance were affected to varying degrees in the mutant.
• Desiccation resistance differed based on growth medium, being stronger in LB but weaker in M9 compared to wild-type.
• Transcriptome analysis confirmed differential expression of resistance-related genes and metabolic pathway alterations.

Conclusions:

• The RpoS sigma factor plays a significant role in the environmental stress resistance of C. sakazakii BAA894.
• Deletion of rpoS impacts multiple stress tolerance mechanisms and cellular properties.
• Findings provide insights into the survival strategies of C. sakazakii in food environments.