Fluoride Accumulation by Streptococcus mutans from a Low Ionic Medium

Abstract

Fluoride binding by Streptococcus mutans in vitro was influenced by the composition of the incubation medium. Accumulation was rapid, sensitive, and irreversible. The remarkable differences between binding at lower (1–8 ppm) and higher (10 ppm and above) exogenous F^- concentrations probably indicated the operation of more than one uptake mechanism. Fluoride binding was remarkedly enhanced by 0.5–5 mM Ca²⁺, and the stimulatory effect of Ca²⁺ could not be demonstrated by its replacement with ions such as Na⁺ and K⁺, and addition of Mg²⁺ to Ca²⁺ resulted in abolition of F^- binding. Ca²⁺-enhanced F^- accumulation by S. mutans may have resulted in receptor site(s) changes leading to covalent bonding of the anion. This study may relate to the cariostatic action of fluoride.

Binding of Fluoride by Oral Bacteria

“…The accumulation of l8F by the assay bacteria was slow and independent of oxy gen, temperature, or an energy source such as glucose confirming the work of other investigators [Kashket and Rodri guez, 1976;Mante and Yotis, 1982;Whitford et al, 1977]. The lack of inhibition of l8F binding by the metabolic poisons 2, 4-dinitrophenol, sodium azide, sodium arsenate, and the ATPase inhibitor N, N'-dicyclohexylcarbodiimide, suggests that active transport did not play any apparent role in the 18F binding process.…”

“…1961;Hamilton, 1977;Kleinberg et al, 1977;Koulourides, 1968;Schachtele, 1977;Silverstone, 1972;Van Houte el al., 1969], Data obtained with the fluoride-selective electrode indicate that a heterogeneous population of streptococci [Jenkins et a!., 1969], Streptococcus sanguis strain H7R33 [Kashket and Rodriguez, 1976], Streptococcus mutans strains FA-1, 6715, and GS-5 [Eisenberg and Marquis, 1981;Gaugleret al, 1981;Luoma and Tuompo. 1975;Mante and Yotis, 1982;Whitford et al, 1977] can bind fluoride. How ever, there is a disagreement as to whether streptococci can accumulate fluoride [Birkland and Rolla, 1972;Birkland, 1973].…”

“…Unless stated otherwise, experimental cultures were grown for 24-48 h in chemically defined media [Socran.s/cy et al, 1973;Terleckyj et al, 1975]. When these cells were treated with 0.5 M HC104 to establish the endogenous fluoride level, use of the fluoride-se lective electrode [Mante and Yotis, 1982] indicated that the cells contained 0.002-0.008 parts/106 when grown in the chemically defined media, or 0.007-0.030 p a rts/10'' fluoride per milligram dry weight of cells when the bacteria were cultured in complex media. To minimize the introduction of flu oride into the assay mixtures and synthetic culture media, chemicals of the highest purity available (Sig ma Chemical Co., St. Louis, Mo.…”

The Role of Cation Bridging in Microbial Fluoride Binding

“…For example, Jenkins and Ed gar [1977] suggested the presence in plaque of ionizable F, bound in a rather strong complex involving organic material and metal ions. Streptococcal fluoride binding has been suggested to be largely internal, with 'loosely' and 'firmly' bound compartments [Kashket and Bunick, 1978;White and Nancollas, 1990], stimulated by calcium and partially abolished by magnesium [Mante and Yotis, 1982], with a pH optimum of 5.0-5.5 [Kashket and Rodriguez, 1976;Yotis et al, 1979] and with a capacity of 50 nmol/g to 300 nmol/g wet weight [Kashket and Rodriguez, 1976;Yotis et al, 1979], If these data do indeed refer to intracellular fluoride, it is clear that the extracellular fluoride binding measured in this work is rather different in character.…”

Interactions of Micromolar Concentrations of Fluoride with Streptococcus rattus FA-1

“…Additional evidence that the accumulation of the DMO" anion is mediated only by the pH gradient and not by nonspecific effects is the reduction of the distribution coefficients by the pH decoupler nigericin (see figure 2). A similar reduction in the pH gra dient was also achieved in oral streptococci using the ionophores gramidicin or valinomacin [Bender et al, 1983;Marsh etal., 1984], Assuming that the fluoride-translocating species is (similar to H* DMO") the undissociated hydrofluoric acid, which is also a weak monobasic acid [Agus et al, 1980;Duschner et al, 1985;Edgar et al, 1981;Eisenberg and Marquis, 1980;Gaugleret al, 1981;Rodriguez, 1976: Luoma et al, 1984;Mante and Yotis, 1982;Whitford et al, 1977], it should be taken up by the bacteria according to the same mechanism. However, the accumulation characteristics of fluoride from acidic media is quite different from that of DMO".…”