The biochemical milieu of the host in the selection of anaerobic species in the oral cavity.

Abstract

The periodontal pocket provides a unique structural site for studies on host/bacterial interactions. The pocket is colonized by a complex but characteristic anaerobic bacterial flora. Many new taxa have been described that have now been supported by comparative rRNA sequence analysis. Within recent years, several molecular approaches have been used to describe both cultivable and noncultivable species, and new genotypes have been reported. Microbial activity rather than the mere presence of a microorganism at a site must be a major factor in the process of disease development. Information on metabolic activities of species and identification of substrates are therefore essential to elucidate the complex interactions that are likely to occur in vivo. We have been using a variety of analytical procedures such as 13C substrate-enrichment nuclear magnetic resonance, 14C isotopic labeling experiments, enzyme assays, impedance measurements, and various chromatographic and electrophoretic procedures to study key species of this predominantly asaccharolytic flora. Results have so far indicated a major role for cationic and anionic acids as sources of energy, but the mechanisms of substrate processing may differ significantly between species. In this ecosystem, crevicular fluid is the likely source of nutrients for species. Components of this fluid appear to have a role in the selection of species in subgingival sites.