Background: Streptococcus pneumoniae is a leading cause of human respiratory tract infection. Despite the lack
of activities of antioxidative enzymes, including cytochromes, hemoproteins, and peroxidases/catalases, traits conferring the
aerotolerant-anaerobic growth of this bacterium are conserved, with high efficacy of antioxidative actions, in an oxygen-rich
Objective: Through proteome analysis, this study’s intention was to evaluate differentially expressed proteins and/or gene
products modeled in a highly virulent strain, S. pneumoniae D39, exogenously-treated with millimolar concentrations of
Method: For two-dimensional gel electrophoresis (2-DE) analysis, following one dimensional isoelectric focusing with an
immobilized pH gradient of pH 4-7, the most significantly mobilized proteins expressed were separated by SDS-PAGE in
the second dimension. With a total of 431 protein spots detected, certain proteins were excised, in-gel trypsin digested, and
analyzed by combination with MALDI-TOF and LC-ESI-MS/MS for mass spectrometric peptide mapping and protein
identification. Utilizing mass spectrometry analysis of spots excised from 2-DE, the selected protein spots were identified
with a variety of databases and MASCOT.
Results: With the aid of comparisons to proteome reference maps, the most differentially expressed 38 proteins, those with
approximately 1.4-fold or more increase and/or decrease or with multiple isoforms exhibiting variable pI values, were
induced by treatment of exogenous 2 mM H2O2. The identified proteins were seen to be involved in pneumococcal
pathogenesis and primary metabolism, amongst others.
Conclusion: This is the first study to convincingly document proteomic information associated with pathophysiological
adaptation under the given oxidative conditions, and corresponding potential antioxidative mechanisms, in S. pneumoniae.