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Determination by Electron Microscope Autoradiography of the Distribution in Plaque of Organisms that Synthesize Intracellular Polysaccharide in situ

1975; Karger Publishers; Volume: 9; Issue: 6 Linguagem: Inglês

10.1159/000260171

1421-976X

C.A. Saxton,

Bone and Dental Protein Studies

The localization and distribution of organisms actively synthesizing intracellular polysaccharide from labelled glucose has been studied in plaque in situ, using electron microscope autoradiography. Freshly extracted teeth were in contact with one of three different glucose concentrations for varying periods of time. After fixation the teeth were prepared for electron microscopy, sectioned, covered with Ilford L4 emulsion and 'exposed' for 10 weeks. Electron micrographs revealed that coccal-shaped organisms predominated in the plaques (ages unknown) and that approximately 30% of the total number of organisms were labelled, thus signifying active polysaccharide synthesis. Although fewer in number than the coccal forms, a greater proportion of the filamentous forms were labelled. Regional examination revealed that the proportion of polysaccharide synthesizing organisms was relatively low at the saliva interface (16%) but increased to 52% in the plaque adjacent to the tooth. Plaques subjected to low glucose concentrations failed to exhibit polysaccharide synthesis in cocci beneath the outer microbial layer at the saliva interface. Filamentous forms continued to be labelled much deeper in the plaque. These observations demonstrate that the proportion of organisms actively synthesizing intracellular polysaccharide in mature plaque is much greater adjacent to the tooth than at the saliva interface. It is suggested that acidic environments would be prolonged at the tooth interface, through the catabolism of the polysaccharide. The filamentous forms, although numerically few, probably contribute significantly to this environment during the absence of exogenous sugars. It is further suggested that the low glucose concentration of saliva would be unlikely to provide sufficient energy for microbial metabolism in organisms situated in the deeper regions of the plaque.