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Differential protein expression in phenotypic variants of Streptococcus pneumoniae
K Overweg1, C D Pericone, G G Verhoef
1Department of Pediatrics, Sophia Children's Hospital, Erasmus University, Rotterdam, The Netherlands.
Infection and Immunity
|July 19, 2000
Summary
Streptococcus pneumoniae phase variation affects virulence. Opaque variants overexpress a protein similar to elongation factor Ts, while transparent variants show higher pyruvate oxidase (SpxB) expression, crucial for nasopharyngeal colonization.
Area of Science:
- Microbiology
- Molecular Biology
- Pathogenesis
Background:
- Streptococcus pneumoniae exhibits phase variation, producing opaque and transparent colony forms with differing virulence.
- Opaque variants are more virulent in systemic infections, while transparent variants excel at nasopharyngeal colonization.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the differential virulence of S. pneumoniae opaque and transparent variants.
- To identify key proteins and their expression levels associated with each colony phenotype.
Main Methods:
- High-resolution two-dimensional protein electrophoresis was used to compare protein expression patterns.
- Mass spectrometry was employed for the identification of differentially expressed proteins.
Main Results:
- Opaque variants overexpressed one protein homologous to Helicobacter pylori elongation factor Ts.
- Opaque variants underexpressed two proteins, including one homologous to Lactocobacillus paracasei proteinase maturation protein (PpmA) and pyruvate oxidase (SpxB).
- Reduced SpxB expression in opaque variants correlates with lower hydrogen peroxide production.
Conclusions:
- The identified protein changes offer molecular insights into the distinct pathogenic strategies of S. pneumoniae variants.
- SpxB's role in hydrogen peroxide production is critical for the efficient nasopharyngeal colonization observed in transparent variants.