THE ACTION OF THYMOL ON ORAL BACTERIA

Several effects of thymol, a plant-derived antimicrobial agent, on Por phyromonas gingivalis, Selenomonas artemidis and Streptococcus sobrinu s were examined. The extremely rapid efflux of intracellular constitue nts evoked by thymol is consistent with its postulated membranotropic effects. Correlations between leakage-inducing concentrations of thymo l and minimal inhibitory concentrations and minimal bactericidal conce ntrations suggest that membrane perforation is a principal mode of act ion of this substance. The thymol-induced decline in intracellular ATP in S. sobrinus appears to be entirely attributable to leakage, wherea s in P. gingivalis thymol may also inhibit ATP-generating pathways. Re lative changes in the transmembrane potential of resting cells of S. s obrinus pulsed with glucose are as sensitive to thymol as is leakage f rom this organism. The effects of thymol on transmembrane potential ar e probably secondary to those arising from leakage of intracellular su bstances.