The specific objective of the proposed research is to delineate the alterations in the physiology of carcinogenic bacteria brought about by fluoride and other trace elements and to identify those trace elements that potentiate the antimicrobial activity of fluoride. Those organisms to be studied are Streptococcus sanguis, S. mutans and Actinomyces viscosus. The elements to be studied are Li, K, Mg, Ca, Sr, Ag, Zn, Si, Sn and F. Those physiological processes which are believed to be important in the caries formation will be investigated. Cell growth will be measured spectrophotometrically; cell viability by plate counts; acid production by the drop in pH of resting cell suspensions in the presence of glucose; acid sensitivity of growth and glycolysis by the determination of what pH those activities cease; transmembrane proton conduction by pH measurements of dense cell suspensions; substrate uptake by radioisotope methods; and fluoride uptake in dense cell suspensions by the space technique.