STUDY ON METABOLIC SYSTEMS FOR PEPTIDES AND AMINO ACIDS OF PERIODONTAL PATHOGENS, PORPHYROMONAS AND PREVOTELLA.

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1. Peptides and amino acids as sources for the growth and the energy production of Porphyromonas gingivalis (Pg) and Prevotella intermedia(Pi)Periodontal pathogens, P. gingivalis and P. intermedia utilized peptides, especially peptides containing aspartate and/or glutamate, as the sources of their growth and energy production. In addition, P. gingivalis preferentially utilized aspartylaspartate and glutamylglutamate, while P. intermedia utilized aspartate and aspartylaspartate. The observation that both bacteria had no dipeptidase activity on their cell surfaces indicates that they incorporate dipeptides through a dipeptide-specific transport system. These findings suggest the existence of segregation or competition between P. gingivalis and P. intermedia for their nutrients.2. Metabolic pathways for peptides and amino acids of P. gingivalis and P. intermediaMetabolic system for peptides and amino acids of P. gingivalis and P. intermedia consists of the following steps: (l) peptide uptake (2) hydrolysis of peptide into amino acid (3) deamination of amino acid into 2-oxoacid (4) oxidation of 2-oxoacid into acyl-CoA and (5) production of short-chain fatty acid. 2-oxoacid oxidoreductases, which catalyze the reaction (4), utilized an artificial electron acceptor, methylviologen. This property is similar to that of enzymes found in archea.3. Molecular biological method for identification of periodontal pathogensFrom the ecological point of view as described 1, a molecular biological method for bacterial identification, was developed to know the distribution in dental plaque of periodontal pathogens, P. gingivalis and P. intermedia. A new method, PCR-RFLP based on bacterial 16S ribosomal RNA gene, was found to be not only simple and fast but also more reliable than the conventional method such as biological and morphological tests.