Plasticity of the Pyruvate Node Modulates Hydrogen Peroxide Production and Acid Tolerance in Multiple Oral Streptococci.

Commensal and are pioneer oral biofilm colonizers. Characteristic for both is the SpxB-dependent production of HO, which is crucial for inhibiting competing biofilm members, especially the cariogenic species HO production is strongly affected by environmental conditions, but few mechanisms are known. Dental plaque pH is one of the key parameters dictating dental plaque ecology and ultimately oral health status. Therefore, the objective of the current study was to characterize the effects of environmental pH on HO production by and HO production was not found to be affected by moderate changes in environmental pH, whereas HO production declined markedly in response to lower pH. Further investigation into the pyruvate node, the central metabolic switch modulating HO or lactic acid production, revealed increased lactic acid levels for at pH 6. The bias for lactic acid production at pH 6 resulted in concomitant improvement in the survival of at low pH and seems to constitute part of the acid tolerance response of Differential responses to pH similarly affect other oral streptococcal species, suggesting that the observed results are part of a larger phenomenon linking environmental pH, central metabolism, and the capacity to produce antagonistic amounts of HO Oral biofilms are subject to frequent and dramatic changes in pH. and can compete with caries- and periodontitis-associated pathogens by generating HO Therefore, it is crucial to understand how and adapt to low pH and maintain their competitiveness under acid stress. The present study provides evidence that certain oral bacteria respond to environmental pH changes by tuning their metabolic output in favor of lactic acid production, to increase their acid survival, while others maintain their HO production at a constant level. The differential control of HO production provides important insights into the role of environmental conditions for growth competition of the oral flora.