Phenotypic variation and modulation in Bordetella bronchiseptica

Area of Science:

• Microbiology
• Bacterial genetics
• Molecular biology

Background:

• Bordetella bronchiseptica commonly displays distinct colonial morphologies on Bordet-Gengou agar (BGA), including domed, hemolytic colonies (Dom+ Scs+ Hly+).
• Variants with flat, non-hemolytic phenotypes (Dom- Scs+ Hly-) arise spontaneously from these characteristic BGA colonies.
• Understanding these phenotypic variations is crucial for accurate bacterial identification and characterization.

Purpose of the Study:

• To investigate the phenotypic and genotypic differences between B. bronchiseptica colonial variants.
• To determine the impact of different growth media on the expression of B. bronchiseptica phenotypes.
• To assess the reversibility of observed phenotypic changes.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was employed to compare whole cell lysates of BGA phenotype variants (BGA-PVs).
• Analysis included surface-exposed proteins, overall polypeptide profiles, and lipopolysaccharide differences.
• Phenotypic expression was monitored across various bacterial growth media.

Main Results:

• SDS-PAGE revealed distinct profiles for Dom+ Scs+ Hly+ and Dom- Scs+ Hly- BGA-PVs, particularly in surface proteins and lipopolysaccharides.
• When cultured on non-BGA media, B. bronchiseptica strains predominantly exhibited SDS-PAGE profiles identical to the Dom- Scs+ Hly- variants.
• Phenotypic changes induced by non-BGA media were reversible upon re-culturing on BGA, irrespective of subculture duration.

Conclusions:

• Cultural conditions significantly influence the phenotypic expression of B. bronchiseptica, including colonial morphology and protein profiles.
• The observed phenotypic plasticity is reversible, highlighting the dynamic nature of bacterial adaptation.
• These findings have implications for understanding bacterial virulence and maintaining consistent bacterial characteristics in laboratory settings.