Phenotypic variation in the Pseudomonas fluorescens clinical strain MFN1032

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Pseudomonas fluorescens is a heterogeneous species with both avirulent and clinically significant strains.
• Clinical strain MFN1032 exhibits hemolytic activity mediated by phospholipase C (PlcC) and biosurfactants (BSs).
• Specific conditions induce translucent phenotypic variants of MFN1032 with defective hemolysis.

Purpose of the Study:

• To analyze the genetic basis and phenotypic characteristics of MFN1032 variants.
• To understand the mechanisms underlying phenotypic variation in this clinical strain.
• To investigate the role of phenotypic variation in virulence potential.

Main Methods:

• Analysis of eight phenotypic variants of Pseudomonas fluorescens MFN1032.
• Genetic analysis focusing on mutations in the GacS/GacA two-component regulatory system.
• Assessment of secondary metabolite production, biofilm formation, and swarming motility.
• Manipulation of intracellular cyclic di-GMP (c-di-GMP) levels.

Main Results:

• Variants clustered into two groups based on distinct phenotypic changes.
• Group 1 variants had mutations in GacS/GacA, impaired biofilm formation, and lacked secondary metabolites.
• Group 2 variants were hyperflagellated, showed enhanced biofilm capacity, lacked BSs, and could not swarm.
• Reduced c-di-GMP restored wild-type biofilm levels but not BS production.

Conclusions:

• Mutations in the GacS/GacA system drive phenotypic variation in P. fluorescens MFN1032.
• Phenotypic variants exhibit distinct alterations in virulence-associated factors like biofilm and BS production.
• Phenotypic plasticity in P. fluorescens may contribute to its adaptability and virulence in clinical settings.