Adenosine 5′-triphosphate (ATP) of Streptococcus mutans GS-5 was studied by the firefly bioluminescence method during starvation in a buffered salt medium. There was a decrease in the cellular ATP content with time. The rate of decrease was significantly greater at 37 °C than at 22 °C. The loss in ATP was not accompanied by a decrease in cell number. This variation may lead to errors in the estimation of viable plaque mass by ATP measurement.

Adenosine 5′-triphosphate (ATP) content and viability of Streptococcus mutans GS-5 were studied in a lactate-acetate buffer at pH 6.5, 5.0 and 4.0 with or without added NaF. Reductions in cellular ATP occurred at all pH values tested, but were most pronounced at pH 4.0 and 5.0 with added fluoride and at pH 4.0 alone. Fluoride at pH 4.0 resulted in the lowest ATP content and was strongly bactericidal, while under all other conditions, no or very delayed cell death was observed. Our findings support the idea that fluoride-mediated transmembrane proton conduction is an important mechanism in the antimicrobial activity of fluoride and that this activity at low pH may be involved in the cariostatic action of fluoride.

SUMMARY The e n z y m a t i c e x t r a c t p t e p a r e d f r o m 48h. r e g e n e r at i n g r a t l i v e r s t a b i l i z e d w i t h d i e t a r y L -t r y p t o p h a n p o s s e s s e s t h e enhanced t h y m i d i n e and t h y m i d y l a t e k inaae a c t i v i t y . The o p t i m a l c o n d i t i o n 8 f o r t h e phoap h o r y l a t i o n o f t h y m i d i n e in vitro were f o u n d and the p O 8 8 i b i Z i t y f o r t h e p r e p a r a t i v e u s e 6 was c o n s i d e r e d . The amount of newly formed t h y m i d

The ATP content of 10 dental plaque samples changed rapidly during starvation in a buffered salts medium. The ATP/mg plaque and ATP/colony-forming unit decreased by 50% during the 1st h of incubation at 37 °C, while viability remained relatively constant. For ATP/mg plaque, the coefficient of variation was least (33.2%) immediately after collection and dispersion and increased thereafter (to 42.6%). Therefore, ATP analysis shortly after plaque collection will provide the most sensitive and reproducible measure of viable plaque biomass.