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Adaptive acid tolerance response of Streptococcus sobrinus
Marcelle M Nascimento1, José A C Lemos, Jacqueline Abranches
1Department of Oral Diagnostics, Dental School of Piracicaba, University of Campinas, São Paulo, Brazil.
Journal of Bacteriology
|September 18, 2004
Summary
Streptococcus sobrinus exhibits an adaptive acid tolerance response (ATR) to survive acidic conditions, crucial for preventing dental caries. Unlike Streptococcus mutans, its acid resistance is not linked to F-ATPase but involves increased glucose PTS activity and altered protein expression.
Area of Science:
- Microbiology
- Oral Health
- Bacterial Physiology
Background:
- Streptococcus mutans and Streptococcus sobrinus are key etiological agents of human dental caries.
- Acid tolerance is a critical virulence factor for cariogenic bacteria.
- While the adaptive acid tolerance response (ATR) of S. mutans is studied, that of S. sobrinus remains less understood.
Purpose of the Study:
- To investigate the adaptive acid tolerance response (ATR) in Streptococcus sobrinus.
- To compare the acid adaptation mechanisms of S. sobrinus with those of S. mutans.
Main Methods:
- Continuous chemostat cultures were used to grow S. sobrinus strains at steady state at neutral (pH 7.0) and acidic (pH 5.0) conditions.
- Acid killing resistance, glycolytic activity, F-ATPase activity, and glucose phosphoenolpyruvate:sugar phosphotransferase system (PTS) activity were measured.
- Proteomic analysis using silver staining of two-dimensional gels was performed on S. sobrinus cell lysates.
Main Results:
- Acid-adapted S. sobrinus (grown at pH 5.0) exhibited increased resistance to acid killing and enhanced capacity to lower pH via glycolysis compared to neutral pH-grown cells.
- Unlike S. mutans, the enhanced acid tolerance in S. sobrinus was not associated with increased F-ATPase activity.
- S. sobrinus grown at pH 5.0 showed a twofold increase in glucose PTS activity, whereas S. mutans showed higher PTS activity at pH 7.0.
- Proteomic analysis revealed significant up-regulation (9 proteins) and down-regulation (22 proteins) in pH 5.0-grown S. sobrinus compared to pH 7.0-grown cells.
Conclusions:
- Streptococcus sobrinus possesses an adaptive acid tolerance response (ATR).
- The mechanisms underlying S. sobrinus ATR differ significantly from those of S. mutans, particularly regarding F-ATPase and glucose PTS activity.
- These findings highlight distinct bacterial strategies for acid adaptation in cariogenic streptococci.