Acid-induced acid tolerance and acidogenicity of non-mutans streptococci.
Acid tolerance and acidogenicity of non-mutans streptococci and their capacity of acid adaptation were studied. The cells of non-mutans streptococci (Streptococcus sanguis [Streptococcus sanguinis], Streptococcus gordonii, Streptococcus oralis and Streptococcus mitis) grown at pH 7.0 showed 0.0088% to 71% viability after acidification at pH 4.0 for 60 min, whereas the cells of mutans streptococci (Streptococcus mutans) were not killed by the acidification. Washed cells of non-mutans streptococci lowered pH to 4.04-4.33 in the presence of glucose, while mutans streptococci cells lowered pH to 3.70. When the growth pH was shifted to 5.5 for 30-90 min, the viability of non-mutans streptococci after the acidification at pH 4.0 for 60 min increased (0.25% to 91%) and the minimum pH values of the cells in the presence of glucose decreased (3.90 4.19). Along with the increase in acid tolerance and acidogenicity, non-mutans streptococci increased activities of H(+)-ATPase and arginine deiminase and amounts of stress proteins cross-reacting with 60 kDa and 70 kDa heat shock proteins (Hsp60 and Hsp70). These results indicate that non-mutans streptococci were capable of increasing their acid tolerance and acidogenicity in response to environmental acidification. Furthermore, it is suggested that the acid adaptation observed in non-mutans streptococci cells could involve the induction of H(+)-ATPase, arginine deiminase and stress protein syntheses. The strains of non-mutans streptococci, which are pioneer bacteria for dental plaque formation and predominant in plaque microbial flora, may play a significant role in shifting the dental plaque environment toward acidic and consequently promoting the colonization of more acid-tolerant and acidogenic bacteria such as mutans streptococci and lactobacilli.
Takahashi
N
N
Department of Oral Biochemistry, Tohoku University School of Dentistry, Sendai, Japan.
Yamada
T
T
D000143:Acids / Q000378:metabolism*; D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000378:metabolism; D003470:Culture Media; D006019:Glycolysis; D006360:Heat-Shock Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D013291:Streptococcus / Q000737:chemistry / Q000201:enzymology* / Q000502:physiology*; D019533:Streptococcus oralis / Q000737:chemistry / Q000201:enzymology / Q000502:physiology; D013298:Streptococcus sanguis / Q000201:enzymology / Q000502:physiology
D000143:Acids; D001426:Bacterial Proteins; D003470:Culture Media; D006360:Heat-Shock Proteins; D006867:Hydrolases; C019723:arginine deiminase; D006180:Proton-Translocating ATPases