A new mechanism of action of fluoride on streptococci

Addition of fluoride to the growth medium of Streptococcus sobrinus resulte d in a loss of glucan-binding lectin activity. Upon removal of fluoride, th e bacteria regained their ability to bind glucan in about one generation. C hloramphenicol prevented recovery of ability to produce the lectin, showing the requirement for protein synthesis. Fluoride also caused a significant reduction in the tendency of the streptococci to form chains of cells, alth ough the spent medium from fluoride-containing growth media did not dechain control cells. The fluoride thus does not activate autolytic enzymes. Impo rtantly, 2-D electrophoresis and SDS-PAGE revealed several proteins were sy nthesized in the presence of fluoride that were not synthesized in its abse nce. It seems possible that fluoride places a stress on the bacteria, causi ng the synthesis of proteins that may play a role in protecting the cells a gainst the stress. Numerous stress proteins are known for bacteria, includi ng those resulting from heat, enzymes and osmotic shocks. The ability of fl uoride to cause loss of glucan-binding may be related to its reported benef icial effects on oral health. (C) 1999 Elsevier Science B.V. All rights res erved.