Morphological, chemical, and antigenic characterization of cell walls of the oral pathogenic strains Actinomyces viscosus T14V and T14AV

The mitogenicity for murine splenocytes of specific surface components of the oral periodontopathic bacterium, Actinomyces viscosus

Many characterized fractions obtained from A. viscosus were examined to identify the macromolecules responsible for mitogenicity for lymphocytes. Spleen-cell suspensions of CBA/J mice were cultured with 50-200 micrograms dry weight of A. viscosus strains T14V and T14AV cellular components. Lipopolysaccharide (LPS) (Escherichia coli) was used as a positive control. Mechanical disruption with a French pressure cell or sonication produced preparations with a stimulation of 69,082 and 45,183 counts above background (CAB), respectively. Mitogenic activity was also present in the culture supernatant (38,000 CAB). Other poorly mitogenic fractions included the peptidoglycan, cell-wall fractions, muramidase digests of cell walls, and the microcapsule extracted from whole cells with 0.5 M MgNO3. The results suggest that mitogenic activity is not associated with the isolated cell-wall structure. The activity was released from the cell surface by physical shearing forces, as well as released into the medium growth.

Binding of 18F by cell membranes and cell walls of Streptococcus mutans

The binding of 18F to isolated cell membranes and cell walls of Streptococcus mutans GS-5 or other bacteria was assayed. The attachment of 18F to these cell envelopes proceeded slowly and reached equilibrium within 60 min. 18F binding was stimulated by Ca2+ (1 mM). The binding of 18F to cellular components was dependent upon the pH, as well as the amount of 18F and dose of the binder employed. The binding of 18F by cell walls prepared from fluoride-sensitive and fluoride-resistant cells of S. salivarius and S. mutans did not differ significantly. The pretreatment of cell walls or cell membranes for 60 min at 30 degrees C with 1 mg of RNase, DNase, or trypsin per ml did not influence the binding of 18F by the walls and membranes of S. mutans GS-5. However, prior exposure of cell membranes to sodium dodecyl sulfate caused a significant reduction in the number of 18F atoms bound by the membranes. In saturated assay systems, cell membranes of S. mutans GS-5 bound 10(15) to 10(16) atoms of 18F per mg (dry weight), whereas cell walls from S. mutans GS-5, FA-1, and HS-6 or Actinomyces viscosus T14V and T14AV bound 10(12) to 10(13) atoms of 18F per mg (dry weight). 18F in this quantity (10(12) to 10(13) atoms) cannot be detected with the fluoride electrode. The data provide, for the first time, a demonstration of 18F binding by cell membranes and walls of oral flora.

Chemical characterization of extracellular polysaccharides produced by Actinomyces viscosus T14V and T14Av

The human isolates Actinomyces viscosus T14V and T14Av produced extracellular polysaccharides in the absence of sucrose. In contrast to strain T14V, strain T14Av produced abundant viscous slime polysaccharide in the culture supernatant fluids when grown in a chemically defined medium containing glucose. After resolution of the T14Av polysaccharides into seven fractions, it was demonstrated that two of these exhibited viscous properties and lacked methylpentose and muramic acid. The major slime polysaccharide purified by gel filtration and ion-exchange column chromatography contained 39% (moles percent carbohydrate) galactose, 37% N-acetylglucosamine, 19% glucose, and 5% mannose. Only trace amounts of protein and phosphorus were detected in this preparation. On the other hand, strain T14V produced negligible slime polysaccharide under the same culture conditions. The major extracellular polysaccharide fraction from this strain contained methylpentoses, hexoses, hexosamines, muramic acid, protein, and phosphorus, suggesting that this fraction might be derived from the cell wall.

Role of macrophages in the lymphocyte response to Actinomyces viscosus

Macrophage cooperation has been considered necessary for lymphocytes to express a variety of their differentiated functions. We attempted to characterize macrophage-lymphocyte cooperation in response to a known periodontal pathogen. Actinomyces viscosus T14V. Using adherent murine cells and subpopulations of splenocyte cultures, we assessed the effect of A. viscosus T14V fractions on lymphocyte proliferation. We determined that (i) various fractions of A. viscosus induced different proliferative responses; (ii) the physical state of the A. viscosus component determined the degree of dependence on adherent cells for proliferation; (iii) the proliferative response to supernatants of sonicated A. viscosus involved interaction among adherent cells and T and B cells; and (iv) the effects of adherent cells on the proliferative response were due to cell-to-cell interactions.

Morphological, chemical and antigenic characterization of M-1 N-acetylmuramidase-digested cell walls of the oral pathogenic bacterium Actinomyces viscosus T14V and T14AV

The cell walls were enzymically solubilized with M-1 N-acetylmuramidase. The minimum amount of enzyme required for maximum response was 70 micrograms/mg of wall. The action of the enzyme seemed localized, producing holes in the wall structure. Chemistry and morphology suggested that all of the wall was solubilized. Antigenically, anti-T14AV formed precipitates with 11-14 antigens from the solubilized walls, of which 3 are unique to strain T14AV. Many of these antigens have not been observed previously due to the physical and/or chemical degradation associated with the extraction procedures. Antisera prepared against strain T14V whole cells formed precipitates with only a few antigens common to both strains. The results suggest that immunological processing and/or surface localization of these antigens are different.