Physico-chemical and structural properties of the surfaces of Peptostreptococcus micros and Streptococcus mitis as compared to those of mutans streptococci, Streptococcus sanguis and Streptococcus salivarius.

The surface properties of nine Streptococcus mitis and four Peptostreptococcus micros strains from the oral cavity were examined and compared with a large group of oral streptococci. Zeta potential and contact angle measurements were employed to determine physico-chemical cell surface properties. In addition, elemental surface concentration ratios were obtained via X-ray photoelectron spectroscopy, and surface structures were examined with transmission electron microscopy. The S. mitis and P. micros strains were found to have higher isoelectric points, higher hydrophobicities and higher N/C surface concentration ratios than some other oral streptococci. The combined data suggest that both species possess large amounts of surface protein. All the S. mitis strains displayed abundant surface fibrils in negative staining, but the P. micros strains were devoid of surface appendages indicating that surface protein is present in different forms in the two species. The surfaces of S. mitis and P. micros type strains differed significantly from the other strains examined.