BACTERIAL ADHESION ONTO APATITE MINERALS - ELECTROKINETIC ASPECTS

The role of the electrokinetic properties of Streptococcus sanguis and Actinomyces naeslundii in determining their adhesion to apatite miner als is examined. It is shown that bacterial adhesion onto a mineral su rface takes place even when both the surfaces are negatively charged, and that the adhered layer is resistant to washing. Also, the mineral fines after exposure to bacteria exhibit zeta potential values which a re in between those of the mineral and the bacteria, but lie closer to that of the mineral. In the absence of salivary proteins, the inorgan ic species present in saliva alter the magnitude of the surface charge but do not affect the bacterial adhesion process. Dissolved apatite m ineral species (in supernatant solutions) are also shown to decrease t he magnitude of the zeta potential of the bacteria. The observed adsor ption of negatively charged bacteria onto negatively charged minerals suggests that electrostatic interactions are not the primary factors d etermining adhesion.