Background: Streptococcus pneumoniaeis 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 the high efficacy of antioxidative actions, in an oxygen-rich environment.
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 H2O2.
Methods: 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.