IADR Abstract Archives
Influence of Arginine With NaF and MFP on Sucrose Metabolism by Streptococcus mutans
Objectives: The effect of arginine on the production of acid by Streptococcus mutans when metabolizing sucrose has been reported earlier (2016 AADR Abstract # 1018). Investigations have now introduced the additive effect of NaF and MFP in this buffering environment. Acid production, as well as the synthesis of lactic acid, were monitored during pH fall experiments, where sucrose served as the carbon source. Detailed theoretical analysis of results was undertaken to access the correlation between pH and lactic acid/lactate formation.
Methods: S. mutans grown in an enriched medium containing sucrose, was suspended in artificial saliva (AS) [3 mM phosphate buffered medium with 6 mM NaCl, 0.2 mM MgCl2 and 1.5mM CaCl2] to which 10 mM sucrose was added. pH fall experiments were conducted under three conditions: cells containing 29 mM (0.5%) arginine alone, cells with 29 mM arginine and 0.5 mM NaF, and cells with 29 mM arginine and 0.5 mM Na2FPO3. Analysis of total lactate was undertaken using a new Ion Chromatography method which permits clear differentiation of fluoride from lactate. The synthesis of lactate/lactic acid was monitored over a 2 hour time period and samples were analyzed for lactate and pH. Theoretical analysis of the data requires the simultaneous consideration of all of the pKa values for phosphate and arginine as well as the ionic strength of the solution.
Results: Resting cells containing arginine lowered the pH to a greater extent than cells exposed to either fluoride agent. Cells with either fluoride agent had lower lactate production early (higher pH) in the experiment but only NaF maintained this trend at later times (lower pH) in the experiment. Detailed theoretical analysis of the data suggests a complex interaction between pH and lactate production with a possible explanation that not all the lactate generated by the bacteria is protonated. Further work is underway to better access this relationship.
Conclusions: Both NaF and MFP, in the presence of 0.5% arginine, inhibited the pH fall of S. mutans. Early work suggests that both fluorides reduced lactate production at higher pH values while only NaF was able to reduce lactate at the lower pH values.
Methods: S. mutans grown in an enriched medium containing sucrose, was suspended in artificial saliva (AS) [3 mM phosphate buffered medium with 6 mM NaCl, 0.2 mM MgCl2 and 1.5mM CaCl2] to which 10 mM sucrose was added. pH fall experiments were conducted under three conditions: cells containing 29 mM (0.5%) arginine alone, cells with 29 mM arginine and 0.5 mM NaF, and cells with 29 mM arginine and 0.5 mM Na2FPO3. Analysis of total lactate was undertaken using a new Ion Chromatography method which permits clear differentiation of fluoride from lactate. The synthesis of lactate/lactic acid was monitored over a 2 hour time period and samples were analyzed for lactate and pH. Theoretical analysis of the data requires the simultaneous consideration of all of the pKa values for phosphate and arginine as well as the ionic strength of the solution.
Results: Resting cells containing arginine lowered the pH to a greater extent than cells exposed to either fluoride agent. Cells with either fluoride agent had lower lactate production early (higher pH) in the experiment but only NaF maintained this trend at later times (lower pH) in the experiment. Detailed theoretical analysis of the data suggests a complex interaction between pH and lactate production with a possible explanation that not all the lactate generated by the bacteria is protonated. Further work is underway to better access this relationship.
Conclusions: Both NaF and MFP, in the presence of 0.5% arginine, inhibited the pH fall of S. mutans. Early work suggests that both fluorides reduced lactate production at higher pH values while only NaF was able to reduce lactate at the lower pH values.