Binding of 18F by cell membranes and cell walls of Streptococcus mutans.

The binding of 18F to isolated cell membranes and cell walls of Streptococcus mutans GS-5 or other bacteria was assayed. The attachment of 18F to these cell envelopes proceeded slowly and reached equilibrium within 60 min. 18F binding was stimulated by Ca2+ (1 mM). The binding of 18F to cellular components was dependent upon the pH, as well as the amount of 18F and dose of the binder employed. The binding of 18F by cell walls prepared from fluoride-sensitive and fluoride-resistant cells of S. salivarius and S. mutans did not differ significantly. The pretreatment of cell walls or cell membranes for 60 min at 30 degrees C with 1 mg of RNase, DNase, or trypsin per ml did not influence the binding of 18F by the walls and membranes of S. mutans GS-5. However, prior exposure of cell membranes to sodium dodecyl sulfate caused a significant reduction in the number of 18F atoms bound by the membranes. In saturated assay systems, cell membranes of S. mutans GS-5 bound 10(15) to 10(16) atoms of 18F per mg (dry weight), whereas cell walls from S. mutans GS-5, FA-1, and HS-6 or Actinomyces viscosus T14V and T14AV bound 10(12) to 10(13) atoms of 18F per mg (dry weight). 18F in this quantity (10(12) to 10(13) atoms) cannot be detected with the fluoride electrode. The data provide, for the first time, a demonstration of 18F binding by cell membranes and walls of oral flora.

The action of selected agents on the accumulation of 18F by Streptococcus mutans.

The action of certain substances known to induce cellular alterations, or encounted in the oral cavity, on the accumulation of 18F by Streptococcus mutans GS-5 has been investigated. A 62-67% inhibition in the number of 18F atoms bound per mg dry weight of cells could be induced by a 15 min pretreatment with 2.7 X 10(-4) M cetyltrimethylammoniumbromide, 1 X 10(-1) M acetic anhydride, or 7 X 10(-2) M HCl. Plate counts indicated that alteration of the cellular composition rather than viability was responsible for this diminution in 18F accumulation. Prior exposure for 15 min of this organism to 1 M HCHO or 0.1 M NaOH did not alter 18F accumulation. Of the common salts encountered in the oral cavity, CaCl2 enhanced 18F binding. Pretreatment of the assay cells for 15-160 min with 0.1-10 mg/ml of trypsin, pronase, protease, alpha-glucosidase, dextranase, or lactoferrin had no significant effect on the accumulation of 18F. However, pre-exposure of cells for 60 min to 1-10 mg/ml of either amylase or lipase induced a 40-67% inhibition in the binding of 18F, while lysozyme enhanced the binding of 18F by the cells. It would appear then that the binding of 18F by S. mutans may be altered by certain substances encountered in the oral cavity.