Journal of Dental Research, Vol 64, 1290-1292, Copyright © 1985 by International & American Associations for Dental Research Online Journals
Fluoride uptake and fluoride resistance in oral streptococci
S. Kashket and R. J. Preman
Fluoride uptake was examined in the highly F-sensitive Streptococcus
salivarius strain 25975, the F-resistant mutant Flr103, and the relatively
insensitive S. sanguis H7PR3. F was taken up by all strains from media at
neutral pH, containing 1 or 10 micrograms F/ml (0.053-0.526 mmol/L), and
uptake was directly proportional to the delta pH that was maintained by the
cells. The final intracellular concentrations of F in the F-resistant
strains were higher than those in the F-sensitive strain. Similar
differences in F uptake were observed in buffer at pH 5.5, although both
delta pH and F uptake were higher in all strains at the lower pH. These
experiments demonstrate that resistance to F does not necessarily involve
the exclusion of F from the cells. The lower uptake of F by F-sensitive
cells is attributed to the finding that F dissipates the transmembrane pH
gradient, and this, in turn, limits the concentration of intracellular F.
