Differential Utilization of Basic Proline-Rich Glycoproteins during Growth of Oral Bacteria in Saliva

Although saliva is widely recognized as a primary source of carbon and nitrogen for growth of the dental plaque biofilm community, little is known about how different oral bacteria utilize specific salivary components. To address this question, 32 strains representing 16 genera commonly isolated from early plaque biofilms were compared for growth over two transfers in stimulated (by chewing Parafilm) whole saliva that was stabilized by heat treatment and dialysis. The cell densities, measured by quantitative PCR (qPCR), ranged from ∼1 × 10(6) to 1 × 10(7)/ml for strains of Streptococcus gordonii, Streptococcus oralis, and Streptococcus mitis and one strain of Streptococcus sanguinis Strains of Streptococcus mutans, Gemella haemolysans, and Granulicatella adiacens reached ∼1 × 10(5) to 1 × 10(6)/ml. In contrast, little or no growth was noted for three other strains of S. sanguinis, as well as for strains of Streptococcus parasanguinis, Streptococcus salivarius, Streptococcus vestibularis, Streptococcus sobrinus, Actinomyces spp., Abiotrophia defectiva, and Rothia dentocariosa SDS-PAGE, lectin blotting, and two-dimensional gel electrophoresis of saliva from cultures of S. gordonii, S. oralis, and S. mitis revealed species-specific differences in the degradation of basic proline-rich glycoproteins (PRG). In contrast, saliva from cultures of other bacteria was indistinguishable from control saliva. Species-dependent differences in the utilization of individual host sugars were minor. Thus, differences in salivary glycan foraging between oral species may be important to cross-feeding and cooperation between organisms in dental plaque biofilm development.