METABOLISM OF ORAL BACTERIA

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Research efforts have developed in two major areas; 1. Characterization of the effect of anaerobiosis on the ultrastructure and surface proteins of gram-negative facultative anaerobes. Findings suggest that anaerobiosis may play an important role in the regulation of bacterial surface components. The results of these studies have been recently published (Infection and Immunity, 1987,55:2320-2323). 2. a. Characterization of the principal components forming the salivary pellicle on gram-positive oral bacteria (Streptococci and Actinomyces). Preliminary experiments involved the incubation of pure cultures of various oral bacterial strains in freshly collected human parotid or submandibular-sublingual saliva, followed by the extraction of adsorbed salivary components with 2%SDS. Salivary components bound to the bacterial surface were identified by SDS-PAGE and immunobloting. The principal salivary components eluted from Streptococcus sanguis were the low molecular weight mucin (MG2) and alpha-amylase, while MG2 was the principal component eluted from other Streptococci and A. viscosus. The MG2 which eluted from the surface of A. viscosus migrated with an electrophoretic mobility similar to asialo-MG2. These observations were verified by examining the interaction between 125I-HSMSL or 125I-HPS with several of the test strains. When 125I-salivary derived pellicles of S. sanguis were analyzed by SDS- PAGE/autoradiography, the autoradiographs were dominated by a component of approximately 55-60 kDa, as well as a low molecular weight band. The salivary derived pellicles from the other bacteria contained several other components of various molecular weights. These data indicate that selective interactions occur between the major salivary secretions and the surface of the bacterial strains tested. A manuscript summarizing these findings is in preparation. b. Characterization of the binding of parotid amylase (isoenzyme B1) to S. sanguis and other oral bacteria. Purified amylase (isoenzyme B1) was prepared from parotid saliva by gel- filtration chromatography, followed by FPLC anion-exchange chromatography. Purity was assessed by electrophoresis and amino-acid analysis. Experiments to determine the specificity of binding of 125I-labelled amylase B1 to S. sanguis and other oral bacteria are in progress.