The effect of human plasma and saliva on co-aggregation between Bacteroides gingivalis and Streptococcus mitis was studied by means of a turbidimetric assay. The co-aggregation activity was obtained from the maximum slope of the absorbance vs. time curve. Its dependence on pH, temperature, and ionic strength was examined, and the number of Bacteroides cells in relation to the number of Streptococcus cells resulting in optimal co-aggregation was established. Co-aggregation inhibition experiments showed that the co-aggregation activity was inhibited by l-arginine and l-lysine, although the activity was unaffected by the sugars tested. Human plasma and saliva were able to inhibit the co-aggregation in a dose-dependent reaction. Plasma exhibited the most potent inhibitory activity in these fluids. Fibrinogen was the most potent inhibitor of the plasma-derived proteins tested. These data suggest the possibility that the oral fluids may modulate the attachment of B. gingivalis to Gram-positive bacteria in periodontal pockets.

Superoxide dismutases (SODs) were purified from extracts of either anaerobically maintained or aerated Bacteroides gingivalis. Each purified enzyme (molecular weight, 46,000) was a dimer composed of two subunits of equal sizes. SOD from anaerobically maintained cells (anaero-SOD) contained 1.79 g-atom of Fe and 0.28 g-atom of Mn, and SOD from aerated cells (aero-SOD) contained 1.08 g-atom of Mn and 0.36 g-atom of Fe. Spectral analysis showed that anaero-SOD had the characteristic of Fe-SOD and that aero-SOD had that of Mn-SOD. Both enzyme preparations contained three isozymes with identical isoelectric points. On the basis of inactivation of SOD by H2O2, it was found that aero-SOD consisted of one Mn-SOD and a small quantity of two Fe-SODs, whereas anaero-SOD contained only Fe-SOD. However, each apoprotein from anaero-SOD and aero-SOD, prepared by dialysis in guanidinium chloride plus 8-hydroxyquinoline, showed only one protein band each with the same isoelectric point on an isoelectric focusing gel. Subsequent dialysis of both apoenzymes with either MnCl2 or Fe(NH4)2(SO4)2 restored the activity. These reconstituted SODs showed only one protein band with SOD activity on native polyacrylamide gel electrophoresis. Furthermore, the two enzymes had similar amino acid compositions, and their amino-terminal sequences were identical through the first 12 amino acids. These results suggest that the three isozymes of anaero-SOD and aero-SOD in B. gingivalis are formed from a single apoprotein.

Exohemagglutinin was found in the culture medium of Bacteroides gingivalis 381. Exohemagglutinin was purified 3,150-fold from culture fluid by ultracentrifugation followed by gel filtration on Sepharose CL-4B and by affinity chromatography on argmine-agarose. Examination of the final preparation of exohemagglutinin by biochemical analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the isolated

In this study, the relationship between enzyme activities involved in oxygen metabolism and the degrees of oxygen tolerance in black-pigmented Bacteroides was investigated. All strains of Bacteroides tested possessed the activities of NADH oxidase and superoxide dismutase, whereas the activities of catalase and peroxidases were not detected in the cell-free extracts. There were relatively high correlations between oxygen tolerance and activity of either NADH oxidase or superoxide dismutase. The activity of superoxide dismutase showed a higher correlation with oxygen tolerance than with that of NADH oxidase. Among the species tested, Bacteroides gingivalis showed the highest activities of both the enzymes and was the most tolerant in the presence of oxygen. Furthermore, the activities of these two enzymes increased during aeration of the oxygen-tolerant strain Bacteroides gingivalis 381, but not in the oxygen-sensitive strain Bacteroides denticola ATCC 33185. These results suggest that superoxide dismutase and NADH oxidase might be important for protection of black-pigmented Bacteroides against the toxic effect of oxygen.

The hemoglobin concentration (Hb index) and oxygen saturation (apparent SO2) in human gingiva were estimated by tissue reflectance spectrophotometry (TRS). The gingiva had significantly lower Hb index and higher apparent SO2 than those in alveolar mucosa, but there was no difference in either parameter among different gingival areas. The reproducibility in repeated measurements was high for both Hb index and apparent SO2 in gingiva. In inflamed gingiva, Hb index was significantly higher than that in clinically healthy gingiva. A lower apparent SO2 was observed in inflamed gingiva. This suggests that the increase in blood supply is insufficient to meet the oxygen demand in inflamed gingiva. There were significant correlations between either the Hb index or the apparent SO2 and the clinical parameters of gingival inflammation such as gingival index, plaque index, Periotron score and probing depth. Thus, TRS may be clinically available to estimate the blood volume and oxygen saturation in inflamed gingiva.