Acid tolerance mechanisms utilized by Streptococcus mutans

Abstract

Since its discovery in 1924 by J Clarke, Streptococcus mutans has been the focus of rigorous research efforts due to its involvement in caries initiation and progression. Its ability to ferment a range of dietary carbohydrates can rapidly drop the external environmental pH, thereby making dental plaque inhabitable to many competing species and can ultimately lead to tooth decay. Acid production by this oral pathogen would prove suicidal if not for its remarkable ability to withstand the acid onslaught by utilizing a wide variety of highly evolved acid-tolerance mechanisms. The elucidation of these mechanisms will be discussed, serving as the focus of this review.

Figure 1. Acid tolerance mechanisms utilized by Streptococcus mutans

Roman numerals denote the particular aspect of acid tolerance each component is involved in: i) the protection and repair of macromolecules; ii) alterations of metabolic pathways; iii) secondary metabolism; iv) cell density, biofilm formation and regulatory systems; and v) intracellular pH homeostasis. AP: Apurinic-apyrimidinic; LGL: Lactoylglutathione lyase; pH_i: Intracellular pH; pH_o: External pH; RR: Response regulator.