STUDIES ON FUSOBACTERIA ASSOCIATED WITH PERIODONTAL-DISEASES

The physiological and metabolic characteristics of representative isol ates of the various subspecies of Fusobacterium nucleatum were investi gated by growing them in continuous culture in chemically-defined medi a. Behaving almost identically, these organisms were found to obtain e nergy from the fermentation of simple carbohydrates such as glucose or fructose or from the fermentation of certain amino acids, free or in the form of small peptides. The latter can be attacked by aminopeptida se activity which was shown to be essential for the growth of the orga nism in an environment lacking fermentable carbohydrate and free amino acids but replete with small peptides. This metabolic versatility may explain the presence of F. nucleatum in both supra- and sub-gingival dental plaque and why it is often found together with organisms such a s Porphyromonas gingivalis which display powerful endopeptidase activi ties. Using the technique of allozyme electrophoresis, the current sub speciation of F. nucleatum was shown to be of doubtful validity and ev idence, based upon physiological and metabolic properties, for differe nces in pathogenicity between isolates was not detected. While this or ganism is a member of various bacterial consortia associated with peri odontal diseases, its contribution to the disease process remains uncl ear.