Surface Characterization of Streptococci

Abstract

     Using electrophoresis, the electron spectroscopy for chemical analysis (ESCA) and the atomic force microscope (AFM), we studied the electrostatic potential, elemental components and ultramicrostructure of the streptococcal surface and investigated the relation between these three elements.
     By measurement of zeta potential, the streptococci were divided into two groups; one consisting of S. cricetus HS-6 and S. rattus BHT, which showed larger zeta potentials and was influenced by pH, and another consisting of S. mutans OMZ 175, S. mutans K-1 and S. sobrinus 6715 which showed smaller zeta potentials and was unaffected by pH.
     ESCA analysis revealed that O, N and C existed on the surface of every streptococci. However P existed only on the surface of the streptococci having larger zeta potentials (S. cricetus HS-6 and S. rattus BHT). This indicates that zeta potentials depend on the surface layer of streptococci.
     Furthermore, bacterial surface observations in water using AFM revealed that S. cricetus HS-6, which is in the larger zeta potential group, showed a rough, needle like surface, while S. sobrinus 6715, which is in the smaller zeta potential group, showed a smoother surface.
     We found it possible to analyze the surface characterization of streptococci by using zeta potential, ESCA and AFM. Furthermore, we concluded that differences in zeta potential of the surface of streptococci depended on the amount of teichoic acid on the surface.